Months after President Trump’s victory in November 2016, Jon Ossoff mounted a long-shot congressional campaign in a historically red Georgia district — and unexpectedly became a symbol of hope for demoralized Democrats as he racked up millions from small donors. When he narrowly lost one of the most expensive House races in history in June 2017, Ossoff promised to return.

“I launched this campaign believing that America can become stronger, more prosperous and more secure only if we stay true to the values that unite us,” Ossoff wrote in The Washington Post days after his loss. “I still believe that, and I’m not done fighting.”

On Monday night, Ossoff stayed true to that vow, announcing a Senate bid that, if successful, would make him the first Georgia Democrat elected to the position in almost two decades. Ossoff, now 32, will formally launch his campaign Tuesday, telling the Atlanta Journal-Constitution that he plans to challenge Sen. David Perdue (R-Ga.), whom he called “a caricature of Washington corruption.”

“What I care about is trying to make a difference in people’s lives,” Ossoff said. “Trying to end this appalling corruption that has infected our political system and fighting the abuse of power. … We need warriors for the people in the United States Senate.”

In a statement to The Post on Tuesday, Perdue’s spokesperson Casey Black described the senator as a “truly a different kind of leader with a proven record of shaking things up and actually getting results.”

“He is working hard every day to change the direction of our country, and he is fighting for Georgians who feel like many in Washington still are not listening to them,” Black said.

Georgia will have two spots in Senate up for grabs in 2020, giving Democrats an opportunity to make gains in a red state where demographic changes are beginning to alter the political landscape. Perdue, a first-term senator and former businessman with close ties to Trump, is up for reelection and fellow Republican Sen. Johnny Isakson announced in August that he is retiring at the end of the year.

The fourth Democrat to set sights on Perdue’s seat, Ossoff is the biggest name to enter the race so far and has secured an endorsement from Rep. John Lewis (D-Ga.). The longtime politician and civil rights leader pledged to “work tirelessly to elect” Ossoff, noting that his 2017 congressional campaign “sparked a flame that is burning brighter than ever, in Georgia and across the country.”

“Georgia and America need Jon,” Lewis said in a statement.

Ossoff, a documentary filmmaker and former congressional aide, rose to unlikely national prominence when his candidacy for Georgia’s conservative 6th District turned into an expensive and hard-fought campaign that even got the attention of Trump.

For his supporters, Ossoff’s campaign, which focused on civility and grass-roots organizing, suggested a new way to defeat Republicans and offered a stark contrast to Trump’s bruising tactics. For a while, it seemed to be working.

Polls ahead of the June 2017 special election had Ossoff and Republican challenger, Karen Handel, neck-and-neck in a district where the previous Democratic candidate had lost by 23 points. Ossoff managed to raise about $30 million, much of which came from “hundreds of thousands of small-dollar donors,” he later wrote in The Post.

“From the beginning I believed that to compete in this district we had to run a different kind of campaign — a campaign that put grass-roots organizing and personal contact with voters above all else,” Ossoff wrote.

But Republicans found success by portraying Ossoff as a “puppet,” whose “strings are being pulled by the Democrats and Nancy Pelosi.” He was labeled an “outsider” — “Not one of us,” declared Handel’s ads, which noted that Ossoff lived just outside a district covering counties north of Atlanta’s metro area, according to Vox. The two candidates poured $60 million into the race with prominent figures such as Trump, Vice President Pence and then-House Speaker Paul D. Ryan (R-Wis.) coming to the state to stump for the GOP, AJC reported.

On June 20, 2017, Ossoff lost to Handel by four points.

“This is not the outcome any of us were hoping for, but this is the beginning of something much bigger than us,” Ossoff said in his concession speech. While Ossoff did not run again in 2018, Handel was unseated by Democrat and political newcomer Lucy McBath. Experts have credited Ossoff with laying the groundwork for McBath to capitalize on the state’s grass roots movement, HuffPost reported.

Ossoff told AJC on Monday that he plans to build on his 2017 campaign during his Senate run, also citing Democrat Stacey Abrams’s historic bid for Georgia governor last year as inspiration. Abrams, who became the first African American woman in any state to receive a gubernatorial nomination from a major party, lost to Gov. Brian Kemp (R) by fewer than 1.4 percentage points. She has ruled out running for Senate.

Ossoff said he was motivated to join the Senate race by a national “crisis of political corruption” and Georgia’s strict new abortion restrictions. He supports banning the sale of assault weapons, legalizing marijuana and universal health care, AJC reported.

In a Monday interview with MSNBC’s Lawrence O’Donnell, Ossoff said he has learned from his failure in 2017.

“I will never be intimidated from telling my own story and touting my own accomplishments because of the inevitable partisan smears that come down from Washington,” he said. “We have to be bold and direct and clear in the face of that kind of intimidation.”

Ossoff faces what will probably be another grueling campaign. Trump beat Hillary Clinton by nearly six percentage points in Georgia, and Republicans continue to dominate at the state level. According to AJC, Perdue’s campaign has raised roughly $5 million so far.