(CNN) When President Donald Trump accused his predecessor, Barack Obama, of ordering a wiretap of Trump Tower during the 2016 campaign, the FBI stayed quiet -- in public. But behind the scenes, its controversial director, James Comey, directed senior staffers to ask the Justice Department to issue an open denial.

The DOJ has not addressed the issue and the FBI has not commented on Trump's assertion, levied baselessly on Saturday, leaving former officials, like Obama administration Director of National Intelligence James Clapper, to deny it on Sunday morning. Trump provided no evidence to support his claim about Obama.

Comey's decision to outsource the pushback might be seen as odd -- and upsetting to critics who are still sore over his camera-ready handling of the Clinton email investigation -- given his reputation for speaking out when the FBI comes under attack or is at risk of being cast in an unflattering light. But the current path is actually a more familiar one: the FBI doesn't normally comment on active investigations.

Indeed, a person familiar with the matter told CNN's Pamela Brown and Shimon Prokupecz on Monday that Comey sought DOJ intervention because he was stunned by Trump's tweets and concerned the accusations -- which he has told the White House are untrue -- could damage the FBI's reputation.

The pressure will rise after Secretary of Homeland Security John Kelly told CNN's Wolf Blitzer on Monday that, while he personally was unaware of any illegal activity, if Trump made the accusation, "he's got his reasons to say it, he's got some convincing evidence that that took place."

For now, Comey, who Kelly called a friend, remains silent. But the question remains: How long will that last?

Entering the 2016 limelight

On July 5, 2016, Comey called a press conference to reveal that he would not recommend charges against Clinton over her use of a private email server during her time as secretary of state. The disclosure came with a number of caveats, in a political sense, as Comey used the forum to sharply criticize Clinton's behavior.

"Although we did not find clear evidence that Secretary Clinton or her colleagues intended to violate laws governing the handling of classified information," he said, "there is evidence that they were extremely careless in their handling of very sensitive, highly classified information."

JUST WATCHED FBI Dir.: Clinton email server "extremely careless" Replay More Videos ... MUST WATCH FBI Dir.: Clinton email server "extremely careless" 03:32

Despite the tough talk, the Clinton campaign was delighted to step out from under the shadow of a potential prosecution. Republicans were less enthused and called Comey to Capitol Hill to discuss it under oath. In his testimony, he said Clinton had been truthful with investigators, but disputed a number of her public statements. He also shot down an accusation from Trump, then the presumptive GOP nominee, that his decision was driven by a deal Clinton had struck with former Attorney General Loretta Lynch.

With that, Comey made his exit from the campaign stage. Or so it seemed. He remained under the radar for more than three months as Clinton seemed to consolidate her lead in the polls ahead of Election Day.

And then it happened.

October surprise

As Election Day approached, Comey's office delivered a letter to Congress on October 28 with word that the FBI had turned up emails from an unrelated case -- one focused on former New York Rep. Anthony Weiner, the estranged husband of close Clinton aide Huma Abedin, as it turned out -- that might have a connection to the Clinton server probe. Trump pounced.

"You can't review 650,000 new emails in eight days. You can't do it, folks," he said at a rally in Michigan after the news broke. "Hillary Clinton is guilty. She knows it, the FBI knows it, the people know it, and now it's up to the American people to deliver justice at the ballot box on November 8."

JUST WATCHED FBI looking into new Clinton emails Replay More Videos ... MUST WATCH FBI looking into new Clinton emails 01:38

Comey explained his reasoning in a message to FBI employees.

"We don't ordinarily tell Congress about ongoing investigations, but here I feel an obligation to do so given that I testified repeatedly in recent months that our investigation was completed," he said. "I also think it would be misleading to the American people were we not to supplement the record."

A week and a day later, in the final frenzied moments of campaigning, Comey returned with one more letter -- this time to clear Clinton. Again. "Based on our review (of the emails), we have not changed our conclusions that we expressed in July with respect to Secretary Clinton," he wrote.

The late flurry enraged Democrats and enlivened Republicans. Trump's stunning victory two days later cemented Comey's place as one of the most divisive figures in government. In the aftermath of the election, especially as new questions surface about the new President's alleged ties to Russia, Comey-watching has become a kind of sport among political observers.

Next move?

Critics of Trump, many of them scorned Democrats, are looking again to Comey -- this time for a smoking gun that connects the White House and Kremlin. Republicans, including those in the Trump administration, seem to regard him with caution, as one of the few people outside the GOP with enough power to cripple this young presidency.

Comey has shown no overriding desire to soothe their fears. When the FBI was asked by White House chief of staff Reince Priebus to dispute reports of contacts between Trump associates and Russians known to US intelligence during the campaign, Comey and his top deputy demurred.

It was an odd ask, even setting aside the awkward fact that the FBI is investigating communications between Trump campaign officials and Russians in the lead-up to the 2016 election. Moscow, at the time, was trying to meddle and help Trump, the US intelligence community had concluded. And while there is no evidence of any coordination between the two sides, Attorney General Jeff Sessions has recused himself from any investigation after a press leak made clear he had met with the Russian ambassador. Trump and Republicans have said they will get to the bottom of the leaks.

Meanwhile, the relationship between the White House and Comey now seems to be souring. Press secretary Sean Spicer refused to say if the FBI boss had Trump's confidence during a briefing on Monday.

"I haven't asked him that yet," Spicer said. "Obviously (Trump is) focused today, first and foremost, on this effort to keep the country safe."

As for Comey, the focus remains on shutting down suggestions that Obama ordered the bureau to spy on Trump. That desire could even lead to yet another controversial public appearance.

"Does he know of a possibility there might be a confrontation and be fired by the President? Sure," a source told CNN. "Does he worry about it? No."