Three weeks ago, Hillary Clinton's lead over Donald Trump was only two points in the head-to-head matchup. | AP Photo Wisconsin poll: Clinton surged after Trump tape

Hillary Clinton leads Donald Trump in Wisconsin, according to a new poll out Wednesday that tracked the fallout of the leaked Trump tape in which the GOP presidential nominee crudely bragged about groping and trying to sleep with married women.

The Marquette Law School poll shows Clinton with a four-point lead over Trump in a head-to-head matchup, 46 percent to 42 percent. Her margin increases in a subsequent question, when respondents are also offered the options of Libertarian Gary Johnson and Green Party nominee Jill Stein: In the four-way ballot test, Clinton leads Trump, 44 percent to 37 percent, with Johnson at 9 percent and Stein at 3 percent.

The poll was conducted last Thursday-Sunday, and it was already in the field when the tape surfaced on Friday. But the poll shows the tape may have had a significant impact on Trump’s support.

About half the interviews overall were conducted Thursday, before the tape was released. In those interviews, Trump actually had a one-point lead in the four-way ballot: 41 percent to 40 percent.

But the race shifted toward Clinton on Friday, when likely voters preferred her, 44 percent to 38 percent for Trump.

And on Saturday and Sunday, Clinton was leading Trump by a yawning, 19-point margin, 49 percent to 30 percent. (The poll was conducted entirely before Sunday night’s debate.)

Three weeks ago, Clinton's lead over Trump was only two points in the head-to-head matchup, and three points in the four-way test.

Meanwhile, the Senate race in the state is tightening, according to the poll: Former Democratic Sen. Russ Feingold’s lead over incumbent Republican Ron Johnson is down to just two points: 48 percent to 46 percent.

In the previous poll in mid-September, Feingold led Johnson by six points, 47 percent to 41 percent.

The poll surveyed 878 likely voters and has a margin of error of plus or minus 3.9 percentage points.