ATLANTA — He became a household name in history's most expensive Congressional race. Now Democrat Jon Ossoff is joining the field seeking to challenge US Sen. David Perdue in 2020.

Ossoff says he'll run to advance health care and environmental issues, among others, and to unseat an "ineffective" incumbent who has advanced the agenda of an "obscene" Donald Trump presidency.

Democrat Ted Terry is already running for the US Senate, as are Democrats Sara Riggs Amico and Teresa Tomlinson. 

Ossoff said Tuesday in an interview that money from gun and pharmaceutical lobbies are controlling legislation, while government scientists are silenced by the Trump administration.  

"We have a crisis in this country of political corruption," Ossoff said.

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The 32-year-old Democrat became a household name in metro Atlanta two and a half years ago when - as a political newcomer - Republican Karen Handel beat him in a close special election to replace Tom Price in Georgia's sixth congressional district. 

Because that election came shortly after Trump's inauguration, Ossoff’s name recognition became national. He announced his 2020 candidacy on MSNBC Monday night – speaking, in part, to campaign donors across America.  

He told 11Alive Tuesday that in 2020, he will try to build on the work done by fellow Democrat Stacey Abrams, when she nearly won the governor's office in 2018.

"I’m going to build a grassroots army across the state - unlike anything this state has ever seen - to defeat David Perdue, and to deliver representation this state can be proud of," Ossoff said. 

It will be another expensive race. Tomlinson is searching hard for campaign money. The former mayor of Columbus, Georgia was raising money in California, Tuesday. She told 11Alive she’s raised money in Chicago, Miami and New York. Friday, she said she's raising money in Washington, D.C. 

She said Abrams near-win last year has raised the interest of national donors.

"That conveys that it is indeed a two-party state. People are very interested. And I can tell you, there’s been a seismic shift in Georgia as people realize that we’re no longer one-party dominated," Tomlinson told 11Alive Tuesday from Los Angeles.

RELATED: Calling Sen. Perdue a 'caricature of Washington corruption,' Jon Ossoff announces Senate run

Add to that the reported interest in Georgia of a SuperPAC supporting President Trump – indicating that Georgia is no longer a lock for Republicans. 

Also influencing the political winds - the US Senate race next year to replace Johnny Isakson, who is resigning at the end of this year because of health issues. The vacancy of Isakson's seat will put a US Senate special election on the same November 2020 ballot as the election for the seat now held by Perdue. Gov. Brian Kemp has yet to name a Senator to fill the position in the interim.

RELATED: Georgia Senate race: What happens after Johnny Isakson resigns?

Ossoff says he never considered vying for that special election seat, in part, because he says he wants to unseat Perdue. 

"He has not come down from his private island once for a public town hall to answer his own constituents," Ossoff said. "He has to go. He’s not effective. He runs errands for the president. He does favors for his donors. And we need change."

The national Republican Senatorial committee tweeted of Ossoff's entry into the race: "Failed congressional candidate @ossoff joins fellow unaccomplished, far-left candidates in the already-crowded and divisive Georgia Dem primary. Welcome to the circus!"