Sanders to launch presidential bid
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Sen. Bernie SandersBernard (Bernie) SandersChris Murphy’s profile rises with gun tragedies Clip shows Larry David and Bernie Sanders reacting after discovering they're related For now, Trump dossier creates more questions than answers MORE (I-Vt.) will officially launch a bid for the White House on Thursday.

A Democratic source close to the senator confirmed to The Hill that Sanders will announce his candidacy for the Democratic presidential nomination in a statement later this week, before heading back to his home state for a campaign kick-off event early next month. 

Sanders will be the first Democrat to formally challenge Hillary ClintonHillary Diane Rodham ClintonChris Murphy’s profile rises with gun tragedies DNC, RNC step up cyber protections Gun proposal picks up GOP support MORE for the Democratic nomination, but he faces long odds. 

The former secretary of State has a huge lead over the field of potential Democratic contenders, taking 62 percent support in the latest Fox News poll released last week.

Sen. Elizabeth WarrenElizabeth Ann WarrenOvernight Finance: Lawmakers grill Equifax chief over hack | Wells Fargo CEO defends bank's progress | Trump jokes Puerto Rico threw budget 'out of whack' | Mortgage tax fight tests industry clout Michelle Obama is exactly who the Democrats need to win big in 2020 Wells Fargo chief defends bank's progress in tense Senate hearing MORE (D-Mass.), who insists that she’s not running for president, came in second at 12 percent, followed by Vice President Biden at 9 percent and Sanders at 4 percent.

Still, many Democrats will be happy to see Clinton get at least a token challenger. They believe it could keep Clinton sharp as she prepares for the general election, and Sanders is a liberal favorite who will challenge her on policy issues from the left.

Vermont Public Radio first reported his decision. 

—This post was updated at 5:15 p.m.