Perriello is set to announce his plan to seek the Democratic nomination Thursday, according to the operatives, who spoke on condition of anonymity because they were not authorized to discuss Perriello's plans publicly. Perriello did not respond to a phone call and text message seeking comment. His decision to run was first reported by The New York Times.
The former one-term congressman from Charlottesville and State Department official's decision to enter the race shocked Virginia's political class late Wednesday. Lt. Gov. Ralph Northam has long been considered the presumptive Democratic nominee and Perriello's kept a tight lid on his interest in running.
A spokesman for Northam did not immediately return calls seeking comment.
Perriello faces an uphill climb. The primary is in June and Northam has effectively been running for nearly two years, raising more than $1.5 million and locking up key endorsements of party leaders like Gov. Terry McAuliffe and Sens. Mark Warner and Tim Kaine.
Perriello was a one-time favorite of his party's liberal wing when he was in Congress and when he flirted with a gubernatorial run in 2013, but has been largely absent from state politics in recent years. He was most recently a special envoy to Africa for the State Department.
Reaction to Perriello's decision to run was mixed among state Democrats. State Sen. Dick Saslaw said Perriello was on an ill-advised "suicide mission" that would only succeed in hurting his party's eventual nominee.
"The only thing he's capable of doing is making Ralph spend some money," Saslaw said.
But former state Del. Michael Futrell, who was a key surrogate to U.S. Sen. Bernie Sanders' presidential run, said the party's liberal voters could gravitate to Perriello over the more moderate Northam, but it's not a foregone conclusion.
"These Sanders supporters, they aren't just looking for names, they're looking to see what you're willing to fight for," Futrell said.
Virginia's gubernatorial contest is expected to be one of the most closely watched races in the country this year, as it will be the first competitive contest in a swing state after Donald Trump's presidential victory.
On the Republican side, former Republican National Committee Chairman Ed Gillespie is squaring off against a former Trump campaign state chairman, Corey Stewart, and state Sen. Frank Wagner.
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