ATLANTA -- Pledging to "root out corruption in politics," Jon Ossoff, a former long-shot congressional candidate who rose to prominence two years ago riding a wave of dissatisfaction with Washington, says he's challenging Republican Sen. David Perdue in 2020.
Ossoff, the fourth Georgia Democrat to join the race that could help determine control of the Senate, announced his bid Monday night during an appearance on "The Last Word" on MSNBC.
"I'm running because we face a crisis of political corruption in this country," Ossoff told host Lawrence O'Donnell, calling Perdue a "caricature of Washington corruption."
Ossoff cited Congress' failure to take up gun control legislation and political influence at scientific institutions as examples of corruption.
Perdue, a former Fortune 500 company chief executive, has emerged as a close ally of President Donald Trump after being elected in 2014.
National Republican Senatorial Committee spokesman Nathan Brand called Ossoff an "unaccomplished, far-left candidate" in a statement.
Rep. John Lewis, the civil rights leader and influential Georgia Democrat, has already endorsed Ossoff in the primary.
Lewis said Ossoff's 2017 campaign "sparked a flame that is burning brighter than ever, in Georgia and across the country." He pledged to work "tirelessly to elect him" to Senate.
The two open Senate seats have raised Georgia's status as a must-watch 2020 battleground.
While Ossoff will face a primary contest in the race for Perdue's seat, the race for Isakson's seat won't have any primary and will instead be open to all qualified candidates, significantly increasing the likelihood of a runoff.
Ossoff, a 32-year-old investigative filmmaker, faced that type of wide-open race in his 2017 special election loss. He won the most votes by far in the 18-candidate race for the suburban Atlanta House seat in April 2017, but fell short of topping 50%, which is needed for an outright win. Ossoff lost the subsequent runoff to Handel.
Others seeking the Democratic nomination in the race against Perdue include 2018 candidate for Georgia Lt. Gov. Sarah Riggs Amico, former Columbus Mayor Teresa Tomlinson and Clarkston Mayor Ted Terry.
The field began to form after Stacey Abrams, former Democratic candidate for Georgia governor, announced in April that she would not run for the seat.
Brand said Ossoff's "extreme left-wing views will fit in with the rest of the crowded Democratic primary but will stand in sharp contrast to David Perdue's positive record of delivering results for all of Georgia."
Ossoff says on a newly launched website that he's "building a movement to mount an all-out attack on corruption in Washington — starting with President Donald Trump and Georgia Senator David Perdue."