When House Democrats present their case to senators about why they should vote to convict President Trump of the impeachment charge that he incited an insurrection in the Capitol, some say their case may be hampered by the presence of Rep. Eric Swalwell as an impeachment manager.

After months of stating falsehoods about the election results, Trump assembled a mass of his supporters in Washington, D.C., and doubled down on his debunked claims. After a rally in which Trump lambasted the Congress that was certifying President-elect Joe Biden's win, a mob of his supporters marched across the city and stormed the Capitol.

Hundreds of lawmakers were forced into hiding as the rioters overwhelmed the Capitol Police. Some chanted "Hang Mike Pence" as the vice president hid nearby. Multiple people died as a result, including one Capitol Police officer.

A week later, Trump was impeached by the House, and Swalwell was given the heavy responsibility of being on the team to present the case against Trump to the Senate in his impeachment trial. The result -- although Trump will be out of office when the trial happens -- could be that Trump is barred from ever holding office again. 

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"America is under an attack incited by President Donald Trump. Lives have been lost and future plans are in place to stop a transition of power," Swalwell said in a statement. "It is a solemn privilege to be named an impeachment manager."

But some don't believe Swalwell, D-Calif., is a serious enough person for the responsibility with which he's been entrusted. 

"Pelosi could have had the House GOP Conference Chair as one of the impeachment managers and instead she went with... Swalwell," Cato Institute staff writer and former Libertarian campaign consultant Andy Craig tweeted. "That you want it to fail is just about the only reason to put Swalwell in charge of anything."

Added Federalist Senior Editor Mollie Hemingway: "I saw a NYT reporter say something to the effect of ... you could tell that Dems were trying to take this impeachment more seriously than the last because they didn't have Schiff as a manager. Uhhhhhhh, Swalwell, anyone?"

Swalwell most recently has been embroiled in a controversy about whether or not he should retain his seat on the House Intelligence Committee after it was revealed by Axios he had longtime ties to a Chinese spy. 

Swalwell has not been accused of any wrongdoing, but was linked with Chinese spy Christine Fang, or Fang Fang, for years. That fact has raised questions about his judgment. Fang helped raise money from others for his 2014 campaign and placed at least one intern in his office. 

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Axios reported that Fang had sexual interactions with at least two Midwestern mayors. Swalwell's office on multiple occasions did not answer questions on whether or not he had sexual or romantic interactions with Fang. His office referred Fox News to a statement it gave Axios. 

Rep. Eric Swalwell, D-Calf., votes to approve the second article of impeachment against President Donald Trump during a House Judiciary Committee meeting, Friday, Dec. 13, 2019, on Capitol Hill in Washington. Swalwell will be an impeachment manager for Trump's second impeachment trial. (AP Photo/Patrick Semansky, Pool)

"Rep. Swalwell, long ago, provided information about this person — whom he met more than eight years ago, and whom he hasn’t seen in nearly six years — to the FBI," the statement read. It added that Swalwell "will not participate" in the story out of concerns about possible classified information.

But outside of Swalwell's history with Fang is his Twitter history. The representative is a prolific tweeter with a track record of being antagonistic to Trump and Republican senators. This was especially true during the contentious confirmation hearings for Supreme Court Justice Brett Kavanaugh. 

Notably, Swalwell in 2018 posted a tweet at 3:24 a.m. on Sept. 20, 2018, mocking Sen. Susan Collins, R-Maine, over her complaints that she and her staff had received threats from those who opposed the Kavanaugh confirmation. 

"Boo hoo hoo. You’re a senator who police will protect. A sexual assault victim can’t sleep in her own home tonight because of threats," Swalwell said. "Where are you sleeping? She’s on her own while you and your [Senate GOP] colleagues try to rush her through a hearing."

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Swalwell later deleted the tweet and apologized: "Sexual assault victims deserve respect. And senators shouldn’t be threatened by the public. I said something stupid and minimized ugly behavior. That tweet is deleted and I’m sorry for that."

In this June 30, 2020, file photo, Sen. Susan Collins, R-Maine, speaks during a Senate Health, Education, Labor and Pensions Committee hearing on Capitol Hill in Washington. Collins, who has long been critical of President Trump, is among the better bets among Republicans to vote to convict Trump at a Senate impeachment trial. (Al Drago/Pool via AP, File)

Collins' office on Monday panned Swalwell's 2018 tweet. 

"Threats like these are wrong. Period," Collins Communications Director Annie Clark said. "The threats aimed at Senator Collins that Rep. Swalwell derisively mocked have since led to three arrests and two convictions. We have no idea why he thought his actions were acceptable."

The offices for Swalwell and House Speaker Nancy Pelosi, D-Calif., did not immediately respond to requests for comment about whether they are worried Swalwell's baggage and temperament might harm the case for convicting Trump of the serious charge against him.

Swalwell won't be the head of the Democrats' efforts in the Senate trial. That will fall to Rep. Jamie Raskin of Maryland, who was one of the authors of the impeachment article accusing Trump of inciting an insurrection. 

The other impeachment managers are Reps. Diana DeGette of Colorado, David Cicilline of Rhode Island, Joaquin Castro of Texas, Ted Lieu of California, Stacey Plaskett of the U.S. Virgin Islands, Madeleine Dean of Pennsylvania and Joe Neguse of Colorado.

Swalwell also has a history of attacking other Republican senators online. 

"Let’s not give @senatemajldr McConnell too much credit by calling him #MoscowMitch," Swalwell tweeted in 2019. "Russia protects its people from gun violence by requiring background checks. Mitch is blocking that here."

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McConnell, R-Ky., last week left open the possibility that he could vote to convict Trump at an impeachment trial. His vote will be key, as it could provide political cover for other Republicans to vote for Trump's conviction too. This would include close McConnell allies like Sen. John Cornyn, R-Texas. 

"Senator @JohnCornyn, listen to the Chief. Keeping people safe is his job. Turns out, it’s also yours, too. But the Chief doesn’t have to count on the NRA to keep his," Swalwell said of Cornyn in 2018. 

Sen. Ben Sasse, R-Neb., is another Republican who is considered a potential vote for Trump's conviction. So is Sen. Mitt Romney of Utah. 

"Ben Sasse remains the Mitt Romney of Susan Collinses: He talks a good game but generally falls into line with Trump at the drop of a hat," Swalwell said in a tweet in October, after a report that Sasse harshly criticized the president in a call with constituents. 

With 50 Democrats expected to vote for Trump's conviction, 17 Republican Senators would need to join them for Trump to be convicted. 

It's unclear when a Senate impeachment trial might start. Pelosi has yet to transmit the article to the Senate, which would trigger the beginning of the trial immediately.

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Senate Minority Leader Chuck Schumer, D-N.Y., said on CBS' "60 Minutes" on Sunday that he wants to ensure an impeachment trial does not interfere with other important business in the immediate aftermath of Biden's swearing-in. 

"Well, we have the trial of the president. That's mandated by law," Schumer said. "Second, there's a very, very real need for President Biden to have in place key people in his Cabinet, the people in charge of national security, the people in charge of domestic security, the people in charge of making sure everyone gets vaccinated as quickly as possible."

He added: "And third, this country is in the greatest economic crisis since the Depression, the greatest health care crisis since the Spanish pandemic flu 100 years ago, and we must pass more relief for the American people. We must do all three and we have to do them all quickly. One cannot stand in the way of the other."

Fox News' Ronn Blitzer contributed to this report.