Hillary Clinton and national press secretary Brian Fallon talking onboard her campaign plane in White Plains, New York, in October 2016. (REUTERS/Brian Snyder, File)

Amid the uproar over President Trump’s controversial statement that he would be willing to receive “dirt” on political opponents from foreign sources, Republicans have fired back that Democrats slamming the president have openly considered doing the same thing.

In fact, Brian Fallon, the press secretary for Hillary Clinton’s unsuccessful 2016 campaign, once said he would have been willing to travel to Europe to confirm dirt about then-candidate Trump.

“Opposition research happens on every campaign, and here you had probably the most shadowy guy ever running for president, and the FBI certainly has seen fit to look into it,” Fallon told The Washington Post in October 2017.

“I probably would have volunteered to go to Europe myself to try and verify if it would have helped get more of this out there before the election.”

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Fallon made the comments as part of the original bombshell Post report that revealed the Clinton campaign and DNC helped fund the research that contributed to the unverified anti-Trump dossier. The dossier itself was authored by a former British spy, Christopher Steele, and contained information from foreign sources -- a point Trump defenders sometimes make in downplaying his associates' willingness in 2016 to receive "dirt" from a foreign source.

Fallon said in that interview he was unaware of Steele or his dossier until after the 2016 election, but added: “if I had gotten handed it last fall, I would have had no problem passing it along and urging reporters to look into it.”

The interview could cause headaches for Democrats now slamming Trump for telling ABC News’ George Stephanopoulos he would be willing to listen to foreign governments if they approached him with information on a political rival.

"I think I'd want to hear it... I think you might want to listen, there isn't anything wrong with listening," the president said.

The president continued in the interview: "Somebody comes up and says, ‘hey, I have information on your opponent,' do you call the FBI?

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"I'll tell you what, I've seen a lot of things over my life. I don't think in my whole life I've ever called the FBI. In my whole life. You don't call the FBI. You throw somebody out of your office, you do whatever you do."

When pressed on the issue by Stephanopoulos, Trump responded: "Oh, give me a break -- life doesn't work that way."

Democrats and Trump critics have pounced on the comments, with a number of 2020 hopefuls leading the charge.

Sen. Kirsten Gillibrand, D-N.Y., a 2020 candidate for president, tweeted: "It's time for Congress to begin impeachment hearings."

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Joe Biden wrote, "President Trump is once again welcoming foreign interference in our elections. This isn’t about politics. It is a threat to our national security. An American President should not seek their aid and abet those who seek to undermine democracy."

"This is just the latest example of what Vice President Biden meant when he said that Mr. Trump is an existential threat to our country," anti-Trump former CIA Director John Brennan wrote on Twitter. "'Unfit to be President' is a gross understatement. @realDonaldTrump is undeserving of any public office, and all Americans should be outraged."

Virginia Democratic Rep. Don Beyer wrote: "Trump just blew way past 'no collusion,' he's broadcasting his willingness to receive help from a hostile foreign power in 2020. He's glad his son didn't call the FBI about Russian help and says he wouldn't call them in 2020. Yes we absolutely need an impeachment inquiry."

Beyer, in May, became the first Virginia Democrat to call for Trump's impeachment. Other political commentators shared his dim view of Trump's comments.

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"Trump goes on TV to solicit next foreign collusion," wrote New York magazine's Jonathan Chait.

"Completely predictable," said CNN contributor Amanda Carpenter. "Don’t you people get it yet? Trump is getting away with campaign finance crimes, collusion attempts and obstruction. Right now. As we speak. Why would he change? Bullies bully until someone with courage, savvy, and might forces them to retreat."

Fox News’ Matthew Borowski and Gregg Re contributed to this report.