Former Vice President Joe Biden Joe BidenMomentum growing among Republicans for Supreme Court vote before Election Day Trump expects to nominate woman to replace Ginsburg next week Video of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral MORE (D) holds a narrow lead in Iowa just days ahead of the state's caucuses, according to a poll released Sunday.

A USA Today/Suffolk University survey of likely caucusgoers found Biden in the lead with 25 percent of respondents indicating that they will support him, while Sen. Bernie Sanders Bernie SandersNYT editorial board remembers Ginsburg: She 'will forever have two legacies' Two GOP governors urge Republicans to hold off on Supreme Court nominee Sanders knocks McConnell: He's going against Ginsburg's 'dying wishes' MORE (I-Vt.) and former South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegBipartisan praise pours in after Ginsburg's death Bogeymen of the far left deserve a place in any Biden administration Overnight Defense: Woodward book causes new firestorm | Book says Trump lashed out at generals, told Woodward about secret weapons system | US withdrawing thousands of troops from Iraq MORE (D) trailed at 19 percent and 18 percent in the poll, respectively.

Sen. Elizabeth Warren Elizabeth WarrenBiden's fiscal program: What is the likely market impact? Warren, Schumer introduce plan for next president to cancel ,000 in student debt The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon MORE (D-Mass.), who has also battled among the top tier in Iowa, sat at 13 percent in the poll, the same percentage of likely caucusgoers who told pollsters that they were currently undecided.

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Another 45 percent remain uncommitted to their top choice, meaning that any of the top candidates could see significant gains or drops in their support levels before next week's caucuses.

No other candidates registered above 6 percent support in the poll, suggesting a clear divide between the top four candidates and the remainder of the Democratic field in the first-in-the-nation caucus state.

USA Today/Suffolk University's poll surveyed 500 likely caucusgoers by landline and cell phones between Jan. 23-26. The margin of error is 4.4 percentage points.