Quick — name the 2016 presidential candidate who was subjected for months to an FBI investigation during last year's U.S. election.

If you answered Hillary Clinton, you'd only be half-right.

As revealed during Monday's House intelligence committee hearing on Russian meddling during the U.S. election, it turns out President Donald Trump was also being scrutinized.

FBI Director James Comey disclosed that the Republican president's campaign was under investigation since July.

The U.S. intelligence service was evidently looking for proof of the Trump team's alleged ties to Russia, an investigation that started four months before the election and remains active.

But while Comey kept the Trump-Russia probe under wraps until now, his disclosure last year about the FBI's investigation into Clinton's email habits dogged her throughout her campaign.

A pivotal declaration came just 10 days before election day, when Comey announced that emails that might be "pertinent" to the investigation were discovered on electronic devices belonging to Anthony Weiner, the estranged husband of Clinton confidante Huma Abedin.

'Vast double standard'

That so much focus was put on Clinton's emails while an FBI Trump investigation was simultaneously being kept secret has outraged some of Clinton's supporters. It has also revived allegations that Comey, a Republican, is acting out of politically motivated bias.

Former Clinton staffer Philippe Reines wrote on Twitter Monday that while the FBI in July 2016 had apparently opened an investigation into Trump but released "nothing public," Comey was wrapping a probe on Clinton's emails and disparaging her that very month.

"Annoying," Reines wrote.

July '16: Comey opens investigation of Trump. Nothing public.<br><br>July '16: Comey closes HRC email, finds nothing - attacks publicly.<br><br>Annoying —@PhilippeReines

Adam Serwer, a senior editor with The Atlantic, tweeted that it was "fascinating" that Comey "only disclosed that one of the two candidates" was under investigation.

Comey says investigation began in late July. Fascinating that he only disclosed that one of the two candidates that were under investigation —@AdamSerwer

"[Comey] spilled the beans on Huma's laptop, but not this?" asked political historian Michael Cohen, author of American Maelstrom.

Speaking from New York, Clinton loyalist Amy Siskind found Comey's disclosure to be "a vast double standard" about how the FBI treats classified information.

Some of Hillary Clinton's supporters are outraged that so much focus was put on her emails while an FBI Trump investigation was simultaneously being kept secret. (J. Scott Applewhite/Associated Press)

She noted that a New York Times headline from Oct. 31 stated the FBI found "no clear link to Russia" following an investigation into Trump's alleged ties to Russian operatives — a conclusion Siskind says was clearly premature given the ongoing investigation. Meanwhile, she said, "email-gate and Clinton's emails" dominated news coverage, to Clinton's detriment.

Comey's last-minute letter about emails was especially galling for Siskind, "versus saying nothing about ... an ongoing investigation on the Trump team," she said.

Approaching Russian election probe in 'open-minded, independent way'​ 1:09

'No rhyme or reason'

Former intelligence officials were perplexed. Why divulge information about one FBI investigation during the campaign but not the other?

"There really is no rhyme or reason for why he talks publicly about some investigations and not others," said Chris Swecker, a former FBI assistant director who has worked with Comey. "The golden rule is you just don't talk about ongoing investigations at all."

A difference in Comey's mind was likely that Clinton's emails were now a matter of public record, said Gary Schmitt, co-director of the Marilyn Ware Center for Security Studies at the American Enterprise Institute.

"It would have been very strange for the bureau to deny an investigation was going on from the Clinton emails when there was all the slop on the table."

The investigation into Trump and his team's possible links to the Russian state, on the other hand, would likely have involved intelligence sourcing of confidential information, "which you would want to keep secret until sufficient facts have been gathered to either indict or not."

Like Swecker, John McLaughlin, a former deputy director of the CIA, rejects the premise that the current director would be compromised politically. He lays some blame on the part of former attorney general Loretta Lynch, who he believes should have tapped her deputy to take over the Clinton emails probe instead of passing it down to the FBI.

He should never have been asked to take responsibility for the investigation. - John McLaughlin, former CIA deputy director

"It's easy to criticize him for what happened, but the truth is, he should never have been asked to take responsibility for the investigation," McLaughlin said.

Monday's hearing yielded other big takeaways. Comey and Admiral Mike Rogers, director of the National Security Agency, confirmed publicly for the first time that the FBI was investigating the Trump campaign's alleged ties with Russia, and whether there was any unlawful collusion. They also told the bipartisan committee there was no evidence to support Trump's unsubstantiated claims that the previous administration had wiretapped Trump Tower in Manhattan.

The July timeline about the Trump-Russia probe was no less startling, though one Democratic legislator who may have already known was Harry Reid.

John McLaughlin, a former deputy director of the CIA, believes former attorney general Loretta Lynch, pictured here, should have tapped her deputy to take over the Clinton emails probe instead of passing it down to the FBI. (Yuri Gripas/Reuters)

Back in October, following the FBI letter about new pertinent emails, the former Senate minority leader accused Comey of deliberately withholding information about Trump's close ties to Russia.

The Nevada Democrat's words, penned in a blistering letter to Comey dated Oct. 30, may resonate even more now with a segment of voters who believe outside forces — whether from Russian meddling or FBI favouritism — tipped the outcome in Trump's favour.

"Your highly selective approach to publicizing information, along with your timing, was intended for the success or failure of a partisan candidate or political group," Reid wrote at the time.

He urged Comey in the letter to release what he called "explosive information about close ties and co-ordination" between Trump's advisers and the Kremlin.

No timeline is set for when the Trump-Russia probe will conclude. Until that time, legislators on Monday asked Comey whether he anticipated escalation. The FBI director is bracing for another dose of attempted Russian meddling in the U.S. electoral system in 2018 or 2020.

The Russians have now successfully "introduced chaos and division and discord," he conceded.

"We have to assume they're coming back."