Former Vice President Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE holds a double-digit lead over President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE in a head-to-head match-up, according to a poll released Tuesday.

Biden, the Democratic front-runner, leads Trump by 12 points in an Investors Business Daily/TIPP poll, with the former vice president supported by 54 percent of poll respondents. The margin is a 1 point drop for Biden over Trump between August and July, when Biden held a 13-point margin over Trump in the same poll.

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Other top Democratic 2020 contenders, Sens. Bernie Sanders Bernie SandersSirota reacts to report of harassment, doxing by Harris supporters Republicans not immune to the malady that hobbled Democrats The Hill's Morning Report - Sponsored by Facebook - Republicans lawmakers rebuke Trump on election MORE (I-Vt.), Elizabeth Warren Elizabeth WarrenOvernight Defense: Appeals court revives House lawsuit against military funding for border wall | Dems push for limits on transferring military gear to police | Lawmakers ask for IG probe into Pentagon's use of COVID-19 funds On The Money: Half of states deplete funds for Trump's 0 unemployment expansion | EU appealing ruling in Apple tax case | House Democrats include more aid for airlines in coronavirus package Warren, Khanna request IG investigation into Pentagon's use of coronavirus funds MORE (D-Mass.) and Kamala Harris Kamala HarrisTexas Democratic official urges Biden to visit state: 'I thought he had his own plane' The Hill's Campaign Report: Biden on Trump: 'He'll leave' l GOP laywers brush off Trump's election remarks l Obama's endorsements A game theorist's advice to President Trump on filling the Supreme Court seat MORE (D-Calif.), also hold leads over Trump, albeit by single digits.

Sanders was supported by 49 percent of poll respondents, compared to 45 percent for Trump, while Warren and Harris led 49 percent to 46 percent for Trump, in a hypothetical general election contest.

Both Biden and Sanders held strong leads over the president among independent voters, according to the poll, with both men winning more than 50 percent of independent voters in head-to-head match-ups with Trump.

Warren, meanwhile, struggled in that demographic, winning the support of just 47 percent of independent voters to 45 percent for Trump.

The match-up polling measured responses from 848 registered voters collected from Aug. 22-30, with a margin of error of 3.3 percentage points.