'This president is a national security threat': 2020 Democrats sound the alarm after Trump says he would be open to accepting dirt on his political foes from foreign powers

"The [special counsel's report] made it clear: A foreign government attacked our 2016 elections to support Trump, Trump welcomed that help, and Trump obstructed the investigation," Warren said, referring to the former special counsel Robert Mueller's report on Russian interference in the US presidential election.

"Now, he said he'd do it all over again," she added in a tweet. "It's time to impeach Donald Trump."

Harris suggested Trump's comments could affect how adversarial nations treat the US.

"China is listening. Russia is listening. North Korea is listening," the Senator tweeted. "Let's speak the truth: this president is a national security threat."

"It's time for Congress to begin impeachment hearings," Gillibrand said on Twitter.

"After seeking and receiving the help of our adversaries to to get elected in 2016, Donald Trump is now essentially calling for an open season on our 2020 elections," the former Obama Cabinet member said on Twitter. "Once again, he's putting his interests above our nation's, and risking and the integrity of our elections."

"The definition of collusion from the man guilty of obstruction," Moulton tweeted.

Swalwell claimed he would not accept damaging information against his political opponents, including Trump, from a foreign adversary.

"Let me make it clear for [Donald Trump]," Swalwell said on Twitter. "I will never take dirt from a foreign adversary — EVEN if it means beating someone as corrupt as you."

Swalwell also challenged Republican lawmakers on Trump's claim that they would have acted in a similar way.

"But Trump said every Congressman would take the help. So, every @HouseGOP member should have to answer this: is Trump right?"

"Let's be clear: Donald Trump is talking about conspiring with a foreign government to win an election — again," Inslee tweeted. "This is dangerous and un-American."

"This is weak and pathetic," Bennet said in a CNN interview. "This is what he's been doing since the presidency."

"He's effectively inviting foreign interference in our election," he added.

"It's not 'oppo research' — it's foreign interference in US elections," Sen. Booker said on Twitter.

"That you would say this is disgraceful," he wrote. "That you would do it from the Oval Office (yet again) proves you're unfit for the office you hold."

"President Trump is once again welcoming foreign interference in our elections," Biden, a Democratic primary frontrunner wrote on Twitter. "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 week Biden and Trump have traded jabs, with Trump calling him "sleepy" and "swampman."