President Trump trails Democratic primary poll leader Joe Biden by four points in a new survey of Wisconsin voters, despite having an approval rating close to the 50% threshold that would suggest he is on track to win the critical swing state in November.

Scoring a repeat victory in Wisconsin is crucial to Trump’s reelection hopes. The Marquette University Law School survey issued Wednesday found that 48% of Wisconsin voters approve of the job Trump is doing, but that the former vice president leads Trump 49% to 45%. The poll of 800 registered voters, conducted Jan. 8-12, showed the former vice president with a small surge in Wisconsin since November when he trailed Trump 47% to 44%.

Despite being impeached by the House, the president’s job approval there has risen steadily, moving from 44% in Marquette University Law School’s January 2019 poll, to 48% in this latest survey. Trump’s approval among independent voters — 44% versus 43% who disapprove — suggests resiliency as he prepares to endure an impeachment trial in the Senate.

In the same poll, Vermont Sen. Bernie Sanders narrowly edged the president 47% to 46%.

Biden, the first choice of Democratic primary voters in the poll, is backed by 50% of independent voters, a key bloc; 41% support Trump. Biden even picks up 9% of self-identified Republicans — Trump is only supported by 3% of Democrats. Biden leads Trump by 24 percentage points among women, although male voters support the president by a similar margin.

In the Wisconsin Democratic primary, the Marquette poll showed Biden with 23%, followed by Sanders at 19%, Pete Buttigieg at 15%, and Massachusetts Sen. Elizabeth Warren at 14%. Overall, the survey had a margin of error of 4.1 percentage points. However, the Democratic subsample that gauged the horse race for the Democratic nomination in Wisconsin had a less reliable margin of error of 6.3 percentage points.

On impeachment: Wisconsin voters are split, leaning toward supporting Trump's position that the House vote to approve two articles against him was unwarranted — 47% approved of the vote, 49% opposed it. Forty-nine percent would not support action by the Senate to convict and expel Trump from office, while 44% would.