An ex-Trump adviser who sparked the US inquiry into Russian election meddling is running for a congressional seat vacated by a scandal-hit Democrat.
George Papadopoulos, who served 14 days in prison for lying to the FBI during the Robert Mueller probe, is running for Katie Hill's California district.
Ms Hill stepped down amid claims of an affair with a Capitol Hill aide.
Papadopoulos pleaded guilty to lying about his meetings with alleged Kremlin go-betweens.
He filed his paperwork on Tuesday for California's 25th district with the Federal Election Commission.
He tweeted this week that he was "smelling blood in the water" because of Ms Hill's resignation.
I’m smelling blood in the water now that Katie Hill has resigned. California’s 25th congressional district is wide open for the taking. Someone has to step up. I love my state too much to see it run down by candidates like Hill. All talk, no action, and a bunch of sell outs.— George Papadopoulos (@GeorgePapa19) October 27, 2019
His wife, Simona Mangiante Papadopoulos, also tweeted a picture of her husband at a lectern, and she commented: "Make California great again!"
Who is George Papadopoulos?
Papadopoulos was the first former Trump aide arrested in the US Department of Justice investigation into an alleged Kremlin plot to sway the 2016 US vote.
He was a London-based petroleum analyst before he joined President Donald Trump's election campaign in March 2016 as a volunteer foreign policy adviser.
Papadopoulos soon made contact with a mysterious Maltese academic, Joseph Mifsud.
The professor told Papadopoulos the Russians had "dirt" on Mr Trump's Democratic presidential rival Hillary Clinton in the form of "thousands of emails".
In the following months, thousands of emails linked to the Clinton campaign were published by Wikileaks.
The young political operative told Mr Trump, then a Republican presidential candidate, and other members of the campaign that he could set up a meeting with President Vladimir Putin ahead of the 2016 election.
American authorities were alerted in mid-2016 after Papadopoulos told an Australian diplomat during a drinking session in a London pub about his meetings with Professor Mifsud.
Papadopoulos falsely claimed to the FBI he had met two individuals with Russian connections before working on the Trump campaign in March 2016.
But in fact he had met them after joining the Trump campaign.
Mr Trump's allies played down Papadopoulos' role, dismissing him as nothing more than a "coffee boy".
Why did Katie Hill resign?
Ms Hill said on Sunday she was stepping down with a "broken heart" even as she denied having an affair with her legislative director, which would violate House rules.
The allegation triggered an investigation by the House of Representatives Ethics Committee.
Ms Hill earlier admitted a three-way consensual romance with a female campaign staff member and her now-estranged husband.
The relationship that Ms Hill acknowledged took place before she was elected, so it fell outside congressional rules on personal relationships.
Nude photos of the congresswomen were published online. Ms Hill has accused her husband, whom she is in the process of divorcing, of trying to humiliate her.
She wrote in her resignation statement: "Having private photos of personal moments weaponised against me has been an appalling invasion of my privacy. It's also illegal, and we are currently pursuing all of our available legal options."
Ms Hill's supporters have said she is being held to a different standard because she is a woman and bisexual.
Another California member of Congress, Duncan Hunter, a Republican, has not resigned despite being indicted on charges of using campaign funds to pursue extramarital affairs with five women.