A new poll from Marquette University Law School shows both Texas Sen. Ted Cruz and socialist Sen. Bernie Sanders surging into the leads of their respective primaries ahead of Tuesday’s critical vote. Cruz has opened a 10 point lead over second-place Donald Trump, while Sanders edges Clinton by four points.

An earlier Marquette poll, released at the end of February, showed Trump leading Marco Rubio and Ted Cruz, who were tied for second place, by 10 points. On the Democrat side, Bernie Sanders and Hillary Clinton were tied.

The latest poll, released on Wednesday, shows Ted Cruz with 40 percent support among likely Republican voters, followed by Donald Trump with 30 percent support. Ohio Governor John Kasich is a strong third, with 21 percent support. The poll, of 471 likely Republican voters, was conducted March 24-28.

The Republican poll was conducted before Wisconsin Gov. Scott Walker formally endorsed Cruz for the GOP nomination.

Interestingly, Trump has shown no movement in his support since the late February poll. In that poll, Trump had 30 percent support from likely Republican primary voters, the same level of support he has in the latest poll.

Cruz, however, has surged over the last month. In late February, Cruz had 19 percent support. In this latest poll he has 40 percent support, an increase of 21 points. Kasich has also more than doubled his support, growing from eight percent to 21 percent.

Generally, then, Trump hasn’t picked up any support from candidates who dropped out of the race since the end of February. That suggests Trump has hit a ceiling of support in Wisconsin and will need an aggressive campaign to win the state.

The poll also suggests Trump has a steep climb in Wisconsin for the general election. Among all voters, 70 percent have an unfavorable view of the GOP frontrunner. More than half of Wisconsin voters, 56 percent, say they would be “very uncomfortable” with Trump as President.

Trump trails Hillary Clinton by 11 points in a hypothetical general election matchup. Kasich leads Hillary in the state by nine points. Hillary and Cruz are tied at 44 percent each.

In the past 10 days, four polls of the contest in Wisconsin have been released, with Cruz leading in three of them. The fourth poll showed Trump with a slim two-point lead over Kasich. The Wisconsin primary is seen as one of the best opportunities for Cruz to beat Trump in a winner-take-most delegates state.

Wisconsin awards 18 at-large delegates to the winner of the statewide votes. Another 24 delegates are awarded to the winner in each of the state’s eight Congressional Districts. These congressional district delegates are awarded to the candidate receiving the most votes in that district. In other words, the district delegates are also awarded on a winner-take-all basis.

It is possible that a candidate could lose the statewide vote but still pick up some delegates by winning one or more congressional districts.

Almost every state remaining in the primary contest awards delegates proportionally. A loss of Wisconsin’s 42 delegates creates a challenge for Donald Trump to amass the 1,237 delegates he needs to have a majority of delegates before the RNC convention in July. A Cruz victory in Wisconsin, then, would raise the odds of a brokered convention in Cleveland.

On the Democrat side, Bernie Sanders leads Hillary Clinton by four points, 49-45 percent. He has gained five points since late February. Most of the poll was conducted before his landslide victories in contests this weekend in Washington, Hawaii, and Alaska. He may get additional support in Wisconsin after those overwhelming wins.