Former Vice President Joe Biden Joe BidenBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Democratic groups using Bloomberg money to launch M in Spanish language ads in Florida Harris faces pivotal moment with Supreme Court battle MORE (D) has expanded his comfortable lead over the 2020 Democratic primary field since his presidential campaign announcement last month, according to a new poll.

The Reuters/Ipsos survey released Wednesday found that Biden's support among Democratic voters has increased 5 percentage points, up to 29 percent.

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He now leads his only close challenger, Sen. Bernie Sanders Bernie SandersOutrage erupts over Breonna Taylor grand jury ruling Dimon: Wealth tax 'almost impossible to do' Grand jury charges no officers in Breonna Taylor death MORE (I-Vt.), by 16 points in the poll. Sanders, at 13 percent, is the only other candidate to register more than 6 percent support among Democratic voters.

Biden trails the Vermont senator among millennial voters, who break for Sanders, 18 percent to 16 percent, over the former vice president, but leads the Vermont senator among all other major demographic groups, according to Reuters.

"[T]here is not a significant anti-Biden bloc of voters split between the other candidates,” Ipsos pollster Chris Jackson said, according to Reuters, adding, “At this moment, Joe Biden is a clear front-runner in the Democratic primary."

Many presidential candidates, including some governors such as Steve Bullock Steve BullockMcConnell locks down key GOP votes in Supreme Court fight Senate Democrats demand White House fire controversial head of public lands agency Pence seeks to boost Daines in critical Montana Senate race MORE (Mont.) and Jay Inslee Jay Robert InsleeBarr asked prosecutors to explore charging Seattle mayor over protest zone: report Bottom line Oregon senator says Trump's blame on 'forest management' for wildfires is 'just a big and devastating lie' MORE (Wash.), were largely unknown by the Democratic electorate, according to the poll, receiving less that 20 percent name recognition among voters.

The Reuters/Ipsos poll was conducted on May 10 and May 13, and contacted 1,132 Democrats and left-leaning independents. Its credibility interval is 3 percentage points.