Understanding Senate Majority Leader Mitch McConnell’s handling of the impeachment trial of Donald J. Trump is easy. For some people, impeachment is about high Constitutional questions. For others, it’s about the balance of power between Congress and the White House. But for the wily Republican from Kentucky, it’s about something much more parochial: control of the United States Senate.

For McConnell, that means ensuring each Republican Senator facing an electoral challenge this year uses his or her moment as a Trump juror to maximum political advantage. In some cases, that means protecting centrists by letting them push to mirror the structure of Bill Clinton’s 1999 impeachment trial. In others, it means giving those facing primaries or short of campaign cash an opportunity to take a star turn in Trump’s defense, raising their profile and boosting fundraising.

The first day of the Senate impeachment trial shows how the high stakes fight is testing McConnell’s abilities to manage his conference’s diverse needs. Late Monday night, McConnell released his draft resolution for an accelerated trial procedure that would have meant middle-of-the-night votes and a speedier end to the theatrics on Capitol Hill. That would help election year Senators eager to be seen as hardline backers of Trump, like Sen. Thom Tillis of North Carolina and Sen. David Perdue of Georgia.

But Sen. Susan Collins, the Maine moderate facing a tough re-election race in November, objected. “My boss and others raised concerns,” says a Collins spokesperson. On Tuesday, when McConnell finally submitted the final rules package, hand-written edits moved the length of opening statements from two to three days, and changed how evidence collected in the House would be treated, increasing the scrutiny to which Trump will be subjected during the trial.

The White House wanted the trial to be condensed to two, 12-hour days and that was the plan as the day began on Tuesday, said a person familiar with the White House legal team. McConnell went along with that request, but when some Senate Republicans pushed back during lunch Tuesday, McConnell acquiesced and the White House said three days would be fine as long as the GOP stayed united, the person said.

Ultimately, McConnell has one immutable truth working to his advantage as he tries to hold his conference together. All Republican Senators share with him the goal of continuing GOP control of the Senate, as that control translates into power of committees that boosts their ability to deliver for constituents, raise campaign cash and win campaigns in 2020 and beyond.

McConnell, for his part, has made no apologies about his role. As he put it on Dec. 17: “I’m not an impartial juror. This is a political process. There is not anything judicial about it. Impeachment is a political decision.” And for McConnell, who in 2018 became the longest serving GOP Senate Leader in history, the most important political priority is holding onto power.

McConnell has been following the north star of Senate control from the start of the impeachment process. On Oct. 16, fully 98 days before the Senate trial would begin in earnest, McConnell gathered Senate Republicans for a buffet briefing in the Mansfield Room steps from the Senate chamber. Walking through a PowerPoint presentation, McConnell and Sen. Lindsey Graham, who served as a House-appointed prosecutor during Bill Clinton’s 1999 trial in the Senate, explained the nuts and bolts of how impeachment plays out and what the Senate rules require. Some of the most robust Trump defenders asked about dismissing impeachment out-of-hand if it arrived in the Senate. McConnell told them the rules required the Senate to consider the charges, a position that protected the centrists.

If Trump had counted on McConnell to be a loyal ally in the Senate, he made a safe bet, but mostly because McConnell knew that doing so was in his and his party’s interests. McConnell routinely ignored questions about Trump’s latest impeachment provocations. He refused to engage on questions if it were appropriate for Trump to solicit foreign help for his domestic re-election bid. In the face of government funding deadlines, he guided Republicans to pass spending bills that comported with Trump’s demands.

Along the way, there were moments that called for breaking with Trump. On Sept. 24, McConnell allowed passage of a non-binding resolution asking the Trump Administration to share a whistleblower complaint that flagged for the Intelligence Community’s watchdog the Washington-Kiev call. At the same time, he took to the Senate floor to urge the Secretaries of Defense and State to release whatever aid Trump had delayed. And when Trump on Oct. 3 asserted that McConnell had told him the call to Kiev was “the most innocent phone call that I’ve read,” McConnell’s staff refused to comment for weeks. Then, on Oct. 22, reporters asked McConnell point-blank about the President’s characterization and McConnell left Trump hanging. “We’ve not had any conversations on that subject,” McConnell told reporters at the Capitol.

The daylight between the pair allowed McConnell’s moderate middle to stakeout a position apart from Trump, whose conduct left many of those suburban voters who broke for Trump in 2016 backing Democrats in 2018. McConnell needs a collation that includes Collins, Colorado’s Cory Gardner and Arizona’s Martha McSally alike if he’s to hold his power, and that means giving them the occasional gap from Trump orthodoxy.

But for the most part, it has been robust defense of Trump that has been in McConnell’s interests. Trump is expected to dominate the political landscape for the next 11 months, and Republicans are wise to link arms with the Republican expected to spend more cash on ads, offices and staff than any other figure in the GOP. The trickle-down help to Senate, House and local candidates cannot be denied; when a volunteer knocks on a door for Trump in the suburbs of Portland, Maine, Collins also wants that helper to have kind words for her, too. Too strong a defection on her part could choke off the backing from Trump, who also controls the Republican National Committee’s spending.

It is because all Republican Senators benefit from McConnell’s success in his strategy that he has been able to keep them on board. And on Jan. 7, as the Senate convened for the first full day of 2020, McConnell made clear he had a firm hold over his conference, even those who may have been inclined to split such as Collins or Sen. Lisa Murkowski, who doesn’t face voters until 2022 and carries her own independent streak. Standing on the same Minton tile that the House impeachment managers would march across, nine days later with articles in-hand, McConnell defiantly declared: “We have the votes.” Which meant, at least at that point, he still had control.

As the trial began in earnest on Jan. 21, McConnell seemed still to be holding together his conference. He made enough hand-written edits to the rules package to keep his Republicans in agreement, at least for the moment, and told lawmakers that he would consider changes to the process after hearing both sides’ opening arguments and Senators’ 16 hours of written questioning.

Even McConnell’s critics expect him to remain formidable. “Anything that requires 51 votes, if he keeps his caucus together, he will win,” Sen. Mazie Hirono, a Hawaii Democrat, told TIME just moments before the trial got underway. “He’s going to push through whatever he wants.” McConnell would sleep much easier if such were guaranteed to be the case by the time the trial ends.

—With reporting by Alana Abramson and Brian Bennett

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Write to Philip Elliott at philip.elliott@time.com.