Former vice president Joe Biden delivers a foreign policy speech in New York in June. (Johannes Eisele/AFP/Getty Images)

A new poll finds that former vice president Joe Biden leads President Trump by 9 percentage points in a hypothetical general-election matchup in Wisconsin, a state Trump narrowly carried in 2016 and that is key to his reelection prospects next year.

Biden leads Trump 51 percent to 42 percent among registered Wisconsin voters in the Marquette University Law School poll released Wednesday.

The poll also shows another Democratic White House hopeful, Sen. Bernie Sanders (I-Vt.), with a slight lead over the Republican president, 48 percent to 44 percent.

And two other Democrats, Sens. Elizabeth Warren (Mass.) and Kamala D. Harris (Calif.), are tied with Trump at 45 percent and 44 percent, respectively.

In 2016, Trump carried Wisconsin over Democrat Hillary Clinton by less than 1 percentage point, helping propel him to an electoral college victory despite losing the popular vote nationally by roughly 3 million people.

Wisconsin is among four states — along with Pennsylvania, Michigan and Florida — that political analysts say are most likely to determine the result of the 2020 election. Many of those analysts point to Wisconsin as the most pivotal.

Biden’s standing there is likely to bolster his campaign’s argument that he is the most electable Democrat against Trump.

The poll also finds Biden the best positioned in the Democratic primary.

He is the first choice of 28 percent of registered Democrats, Democratic-leaning independents and independents who don’t lean toward either party.

Sanders is second with 20 percent, followed by Warren with 17 percent; South Bend, Ind., Mayor Pete Buttigieg with 6 percent; Harris with 3 percent; and technology entrepreneur Andrew Yang with 2 percent. All other Democratic hopefuls received 1 percent or less.

The Marquette poll of 800 registered voters was conducted between Aug. 25 and Aug. 29. It is said to have a margin of error of plus or minus 3.9 percentage points for the general-election matchup and 5.3 percent for the Democratic primary question.

Scott Clement and Dan Balz contributed to this report.