The Tennessee Republican senator, who had emerged as a pivotal swing vote in the impeachment trial of President Donald Trump, had finally broken his silence last Thursday evening and submitted a question to Chief Justice John Roberts. But instead of directing it to the President's lawyers, Alexander put his question to the Democratic House managers.

The move set off alarm bells among Republicans, who took it as a sign that Alexander was considering voting in favor of calling for witnesses.

But the wrong box had been checked on the question card he'd sent to the dais. Alexander hadn't meant to put his question to the Democrats — he'd wanted it posed to the President's lawyers, just as most of his GOP colleagues had. As Rep. Zoe Lofgren, a veteran California Democrat who participated in the last three presidential impeachments, began to respond, Alexander quickly walked to the back of the chamber to confer with a top aide of Senate Majority Leader Mitch McConnell, his friend of 50 years.

After a brief conversation, the aide went straight to her boss, whispering something to McConnell and then scribbling on a sheet of paper. Soon after, McConnell piped up with a question of his own, asking the White House counsel to respond to Alexander's query.

"McConnell rescued me there," Alexander said in a subsequent interview.

Sen. Lamar Alexander (R-TN) walks from the Senate subway to the Senate chamber to cast a vote in the Senate impeachment trial of President Donald Trump.

Alexander's question appeared to suggest he was considering thwarting Trump and backing witnesses, but had it been directed at the President's team would have revealed the exact opposite — a sign of where Alexander would ultimately end up later that night.

The episode illustrates the crucial role, both in shaping the big picture strategy and handling the little things, that McConnell played throughout the impeachment trial. While the ultimate outcome always seemed assured — there was never any serious doubt the President would be convicted or removed — the road to end of the trial was bumpy.

McConnell led a party-wide effort in the Senate targeted to ensure that two Republicans, Alexander and Sen. Lisa Murkowski of Alaska, would ultimately vote with the rest of their conference against witnesses. The leader relied on moderates up for reelection in 2020 to make the case to senators on the fence, as well as conservatives like Sens. Mike Lee of Utah, Ted Cruz of Texas and Lindsey Graham of South Carolina to work behind the scenes to guarantee that nothing -- including the President and his Twitter feed -- pushed their colleagues in the opposite direction.

In many ways, McConnell's navigation of the impeachment trial mirrored Brett Kavanaugh's confirmation, in which the Kentucky Republican held his senators together through a sexual assault allegation, a second confirmation hearing and an extended FBI investigation that put Kavanaugh on the Supreme Court but left the Senate bitterly divided.

As he did then, this time around, McConnell gave his conference enough room to operate. It's telling that, in the end, many Republican senators acknowledged what the White House and House Republicans would not: that Democratic House managers proved Trump had indeed engaged in a quid pro quo by conditioning US aid to Ukraine on investigations into former Vice President Joe Biden. But they concluded it didn't matter — that conduct, if inappropriate, simply didn't warrant removal from office.

McConnell didn't press too firmly. He didn't know, for instance, which way Alexander was going to vote on witnesses until hours before he announced his decision. Alexander confided in McConnell that night in what was one of the first conversations between the two close friends during the entire impeachment trial.

"He knows better than to try and tell me how to vote," Alexander said.

Senate Majority Leader Mitch McConnell, R-Ky., leaves the chamber after leading the impeachment acquittal of President Donald Trump.

The story of how McConnell brought the third impeachment trial in US history to a swift end is based on interviews with more than three dozen senators, aides and administration officials, who explained how the Senate leader kept enough of his conference together. Even a bombshell dropped in the middle of the trial — former national security adviser John Bolton's draft book manuscript saying Trump told him of the quid pro quo — did not convince enough Republicans to hear from Bolton or any other witnesses.

It's perhaps an infuriating conclusion to the impeachment trial for Senate Democrats and the House impeachment managers who meticulously presented their case over a 24-hour period: they felt the charges against Trump were proven, and it didn't matter. In his closing argument on Monday, Rep. Adam Schiff, the lead House impeachment manager, said Republicans will be tied to Trump "with a cord of steel and through all of history."

In the end, a sole Republican, Mitt Romney of Utah, agreed with Democrats, voting to convict Trump on abuse of power. Romney was the first senator in US history to vote to convict a President of the same party. His decision put an asterisk on the trial for McConnell and Trump, denying the President the vindication that the impeachment votes were completely partisan in both chambers.

In some ways, Romney's vote was a biproduct of McConnell's efforts to keep his chamber together. But it didn't change the outcome of the trial the way a vote for witnesses would have.

Setting the stage for a partisan trial

The arc of the Senate's impeachment trial was charted months before the House impeached Trump on December 18 . On September 25, a day after House Speaker Nancy Pelosi announced the House impeachment inquiry, McConnell's reelection campaign raised money online pledging to stop it . McConnell pledged "total coordination" with the White House in a December 12 interview with Fox News' Sean Hannity, an interview McConnell gave to stem concerns from conservatives.

Moderate Senate Democrats greeted the initial launch of the House inquiry with trepidation. No one believed the President would actually be removed from office — the votes wouldn't materialize. But as Democratic senators watched their colleagues in the House uncover new details of the President's dealings with Ukraine, some started to believe they could win a political victory even if it fell short of removing Trump from office.

That meant calling witnesses.

US Senate Minority Leader Chuck Schumer (D-NY) speaks to reporters during the first day of the Senate impeachment trial.

By the time impeachment landed on the Senate's doorstep, Senate Minority Leader Chuck Schumer had what he thought was a pretty good plan. Rather than try to convince the American people that Trump should be ousted, the Democrats would focus on convincing them — and four Republicans — that the country deserved a fair trial, including the new witnesses.

Moderates on both sides had hoped that McConnell and Schumer could hammer out an organizing resolution that would result in a 100-0 vote, just like the one in the Clinton impeachment trial, to set the rules.

But by the end of December, McConnell's comments on Hannity and Schumer's response shattered any moderate hopes that a bipartisan agreement on trial rules could be found.

One Democrat familiar with Schumer's strategy and internal party deliberations said after that moment, there was "never a revolt or a rebellion" among Democrats over how to handle the trial. "I've been part of plenty of uncomfortable moments in the caucus," the senator said. "This wasn't one of them."

Senate gangs don't materialize

On the eve of the trial, the Democrats were united. They were hoping the Republicans were not. As new reports continued to drip out over the President's dealings with Ukraine, Democrats thought there could be a rare opportunity to peel off a bipartisan group, a gang with just enough votes to get witnesses and give Democrats a moral victory to carry into the election.

After the impeachment vote, there was a sense that at some point bipartisan conversations would begin between moderate Republicans and the Democrats that have relationships in the Senate.

But as each day passed, those conversations never materialized, to the shock of some Democrats.

One Democratic senator told CNN a Republican colleague had canceled dinner plans, saying it just wasn't the right time. Another Democratic senator recounted being asked, politely, not to approach a GOP colleague on the floor in full view of the press in the gallery. The conversations would be better held out of view.

One Democratic aide said that Democrats were especially wary of engaging too much with Sen. Susan Collins, a Maine Republican many had been disappointed by because of her vote to confirm Kavanaugh.

The Senate trial began January 21 with a marathon session, ending at nearly 2 a.m. ET, after Democrats forced 11 amendment votes on subpoenas for acting White House chief of staff Mick Mulvaney, Bolton and others. One by one, the amendments were all voted down, including by key Republican moderates -- an early sign of the direction the trial was headed.

For Senate Democrats who had spent weeks hoping just a few of their Republican colleagues would take a different path, it became clear that there would be no chance for a bipartisanship. While members talked to friends and colleagues during breaks or at morning hearings, most identified early on there was no convincing the other side. No "gangs" — famous in Senate lore — formed to force a vote on witnesses or take an exit ramp and vote for censure.

Even during the heated Kavanaugh confirmation, Sens. Chris Coons, a Delaware Democrat, and then-Sen. Jeff Flake, an Arizona Republican, came together to hammer out an extended FBI investigation before a confirmation vote.

No such agreement materialized this time. In a body where bipartisan relationships have saved the Senate from the brink many times before, aides and members say there was not even a guise that goodwill or long-forged relationships could save the Senate from a partisan trial.

"It has just been a lot harder over the last two weeks to have conversations with Republican friends," said Sen. Chris Murphy, a Connecticut Democrat with relationships with several GOP senators. "And unfortunately there weren't a lot of levers available for us to press in this trial."

Republicans, however, put the blame at the feet of House Democrats, saying their hand was forced by the partisan, rushed impeachment.

Republicans struggle through the Bolton bomb

After the first week of the trial, Republicans felt good. The party's conference was united in the Senate. While at the White House, Trump and his aides felt the nearly five-month impeachment saga was in its final stretch.

On the Sunday evening before Trump's lawyers planned to deliver their final opening arguments, there was a relaxed atmosphere inside the West Wing. The speeches were set. Aides were optimistic. Confidence was high. And while the stain of being impeached would remain, there appeared to be enough votes in the Senate to block witnesses, putting the conclusion of the trial in sight.

Then the bomb dropped.

Former National security adviser John Bolton leaves his home in Bethesda, Md. Tuesday, January 28, 2020.

The first tremor came when reporters for The New York Times reached out to the White House press office with a request for comment: John Bolton, the onetime national security adviser, had written in his manuscript that Trump directly tied a hold on security assistance to Ukraine to investigations he wanted announced on his political rivals.

The timing couldn't have been worse for Republicans. The news struck at the heart of the impeachment debate just as senators were weighing whether more evidence was necessary to convict or acquit. And after months of sticking together, it seemed the GOP might be undone by one of its own. Bolton, a longtime conservative firebrand, appeared to be breaking rank.

It caught McConnell and his Senate allies by complete surprise, and threw the President's relatively placid defense team into triage mode. Aides huddled in emergency sessions. Someone had to phone the President, who quickly denied Bolton's account. Republican senators who had been defending Trump's actions for months were angry and unsure what to do next.

The President's attorneys started counting, fearful they had just lost a slim advantage that would block witnesses from testifying. Two Republicans, Collins and Romney, had already signaled they were inclined to hear from witnesses. Now, there was fear of a jailbreak. Rather than four, the President's team now worried there could be as many as eight senators who would want to hear from Bolton.

After working late into the night, the legal team gathered at the White House on Monday morning before climbing into Suburban SUVs and black vans for the short drive to Capitol Hill. There they set up shop inside Vice President Mike's Pence's office, a small, cramped room that didn't seem to have enough space for the legal team, their deputies, multiple White House officials and Republican lawmakers who wanted to join them. Some could barely see the televisions from where they sat.

As the President's attorneys addressed the audience of 100 senators in the Senate chamber, the President, dialed into the line in Pence's office, was not happy. He complained repeatedly as his attorneys presented their case, chastising them for speeches he griped were too boring, not compelling and lacked passion.

As Republicans looked for solutions to the Bolton problem, several conservative senators pitched the White House on that idea of sending over the unpublished Bolton manuscript. That way, Senators could view it in a classified setting, giving them the cover they needed to vote against witnesses, knowing they wouldn't be surprised when the book came out in the spring.

The proposal was quickly shot down. One GOP senator told CNN national security adviser Robert O'Brien made it clear that providing the unpublished manuscript wouldn't be possible, given both the national security concerns and copyright issues that could be raised by the publisher and author.

'Take a deep breath': McConnell eases concerns

McConnell waded into the Bolton chaos with a steady hand. At lunch on Monday of that week, McConnell's message was simple: the conference would have an opportunity to vote on witnesses later that week. No one had to make up their mind in the heat of the moment. "Take a deep breath," he said.

A day later, McConnell convened his members again to make clear that the votes to block witnesses weren't there yet, a tactic to remind his members that there was little room for them to vote for witnesses as a means to make a point about good governance.

Senate Majority Leader Mitch McConnell, R-Ky., leaves the chamber after the vote on the motion to allow additional witnesses.

"He drove the point home that more witnesses would be a never-ending trial for us," one Republican member said, adding it was the first time in a year he'd recalled seeing McConnell push. "He wasn't nervous. He was very firm. He was very specific."

McConnell wouldn't keep his entire conference together. Collins and Romney had already signaled they were planning to vote for witnesses, and Romney made clear behind closed doors that he would not be talked out of it — an early sign of his ultimate vote to convict Trump on one of two articles.

"We still had a few hours of the final Q&A to go and Mitt Romney did say that 'the percentage I am going to vote for witnesses is 100%. Don't try to convince me otherwise,'" one Republican senator said. "Mitch said something really funny like, 'Oh yeah, we don't have you in the undecided category, Mitt.'"

McConnell could afford to lose Romney and Collins. Murkowski and Alexander were a whole other ballgame.

McConnell's legal eagles

As he prepared for the trial, McConnell made a consequential decision: he deputized a trio of conservative lawyers in his conference to serve as de facto liaisons to the White House.

Lee, Graham and Cruz, all respected lawyers in the conference, met regularly with Trump's legal team and at times the President himself, seeking to guide the planning and preparation for what was to come. They were part of a group McConnell had dubbed the "legal eagle" team to help develop the conference's strategy. The group also included Sens. John Cornyn of Texas and Mike Crapo of Idaho.

Sen. Lindsey Graham (R-SC) speaks to the media following a break during the Senate impeachment trial on January 29, 2020.

McConnell and Graham both spoke regularly with Trump during the trial, playing different roles, according to people familiar with the conversations. Graham was a sounding board for Trump -- someone who would listen to him vent as he tried to convince him that a shorter trial, one with no witnesses, was the best path forward.

McConnell was a firmer hand, making clear at separate points that he knew his conference best and would be the one guiding the process from start to finish. The dual track effort, people said, served to assure Trump, and, perhaps most importantly, keep him far away from any outbursts directed at wavering senators.

McConnell told the White House they needed to take impeachment seriously. At one point, he delivered the message directly to the President's son-in-law Jared Kushner, and made clear the White House senior adviser needed to look closely at what Clinton's team did, including developing a messaging strategy.

For Cruz, whose history with both McConnell and Graham could charitably be described as uneven at best — Graham once joked about Cruz getting murdered on the Senate floor — it was a role he embraced.

The Texas Republican became a vocal presence during closed-door conference lunches, laying out legal theories and procedure. He launched a podcast that, improbably, became the most downloaded in the country on iTunes. His arguments privately were often designed to corral his colleagues toward a specific end game: blocking additional witnesses.

Cruz made clear, first privately to McConnell, then to the conference more broadly over several meetings, that any agreement to move forward on witnesses would include more than just a subpoena for Bolton. It would include subpoenas for Hunter Biden. And the whistleblower. And perhaps Joe Biden, too.

The message wasn't subtle: Go down this road and it will get messier by the day. It won't be quick, nor will it be easy.

The argument resonated with much of the conference, which to a large degree began repeating it publicly after the Bolton news broke. If the House managers were going to get their witness, then the President was entitled to his as well.

Still, there was work to be done to ensure the handful of fence-sitting Republicans came to the view shared by GOP leadership. The final real opportunity would come during the 16-hour question-and-answer period.

Over the course of several days, a group of Republicans repeatedly disappeared to draft questions in real-time they thought would bolster the White House case with Murkowski and Alexander.

On Wednesday, the first day of questioning, while making the case for Bolton to appear as a witness, Schiff inadvertently gave Cruz and Graham an idea. Schiff argued it was necessary to hear from Bolton, since the White House disputed his account.

But what if it didn't? What if the President's lawyers simply acknowledged that Bolton's recollection may be accurate? Why would you need witnesses?

As Schiff spoke, Cruz and Graham immediately looked at each other from their seats in the Senate chamber. Jay Sekulow, the President's personal attorney, also popped his head up at the assertion. Cruz quickly walked into the cloakroom to get the exact transcript of what Schiff said.

"What if we get the White House to stipulate to this?" Cruz asked Graham in the cloakroom. "Do you think this is something that could get Lisa and Lamar's vote?"

Graham was interested, and the two looked over to see Alexander also in the cloakroom. Alexander was interested, but non-committal. The pair then spoke to Murkowski, who indicated it was an issue she was interested in exploring.

Cruz and Graham continued working through the language of a possible question, staying in the cloakroom nearly an hour after the trial had adjourned for the night on that Wednesday to try and reach an agreement.

The key would be to get the White House to do what it had refused to do at every turn up to that point: acknowledge that there was a possibility a quid pro quo may have occurred, but make clear that even if it had, it wouldn't merit an impeachable offense.

"The White House lawyers for a long time dug in on the argument that there is no quid pro," Cruz recalled, noting that given disputed testimony and the White House chief of staff's own acknowledgment of a quid pro quo, it was a tenuous argument to make from the start. Cruz gave his blunt assessment to the White House team.

"Out of 100 senators, zero believe you on the argument there is no quid pro quo," Cruz said he told the defense counsel. "Stop making it."

Patrick Philbin, the deputy White House counsel, would eventually walk to microphone and, somewhat grudgingly, answer the question from Graham, Murkowski and others, by making the point that even if Bolton's recollection of events was, in fact, true, it wouldn't merit an impeachable offense.

Getting to no — GOP secures the votes to end the trial

From the outset, Alexander was seen by both sides as the linchpin to the vote on whether witnesses would appear. McConnell's strategy was simple: leave him alone.

Alexander kept to himself for most of the trial, writing in his journal and taking meticulous notes. Even his staff had been careful not to steer his reading materials in too strong a direction. Before the trial started, Alexander had called his friend and fellow Tennessean, Jon Meacham, the author of "Impeachment: An American history" to discuss the history of impeachment in the country. Just hours before Alexander made his final decision on witnesses, it was Meacham's book that was on his desk in the chamber.

"He doesn't really decompress with anyone," a source close to Alexander told CNN. "McConnell knows not to put pressure on Lamar. He also knows how Lamar looks at things from a historical perspective. He has been wise not to do much or say much that is aimed at Lamar."

Reporters try to get a statement from Sen. Lamar Alexander (R-TN) as he passes by during a recess in the Senate impeachment trial of President Donald Trump on January 30, 2020.

Alexander's team reminded the White House that a phone call from the President wouldn't be appropriate or effective. And so, the conference waited.

By 6:30 p.m. on Thursday, January 30, 10 days into the impeachment trial, it was still anyone's guess where Alexander was going to come down on witnesses. His staff had two statements at the ready for whichever direction their boss chose to go.

Still camped up in Pence's office, the White House team was equally in the dark over Alexander. Aides and officials had spent the week alternating between sitting quietly while the President's lawyers spoke on the Senate floor, and making sarcastic remarks when it was the House managers' turn. By the time Alexander announced he would be releasing a statement that night, the mood inside Pence's office was that Alexander would vote to allow witnesses. Aides began preparing accordingly.

On most nights, Alexander joined his colleagues for dinner, but that evening, he stole away to his hideaway on the third floor of the Capitol, slipping by with Republican Sen. Lisa Murkowski close behind him. He told Murkowski how he would vote, without lobbying her. They went back down and had guacamole and chips, recalled Alexander. She would come to the same conclusion a day later.

Murkowski had more of a dialogue with McConnell before she made her decision. McConnell did his best to accommodate the Alaska Republican: Murkowski, Collins and Romney got the first question when the Senate began interrogating the legal teams.

Despite Trump's protests, Alexander believed the President did what Democrats alleged: pressured Ukraine to investigate Biden, while using military aid as leverage. Alexander just believed it was inappropriate, not impeachable, conduct.

Alexander said that Ken Starr, the former Clinton special prosecutor, made the most effective argument that the offense did not deserve the punishment — and the House failed with a partisan proceeding. "He focused not on quid pro quo," Alexander said. "He focused on what's an impeachable offense? What did the Founders expect? What about a partisan impeachment? What about James Madison saying that, in effect, there should never, ever be a partisan impeachment? I thought that was the argument."

That helped Alexander settle on the fact that Bolton, whose revelations had upended the trial, did not need to testify.

"If you've got eight witnesses proving that you left the scene of an accident, you don't need nine," Alexander said. "The more successful the Democratic house managers were, the less need there was for me to vote for more evidence."