A new Wisconsin poll shows that Ted Cruz now leads Donald Trump in advance of the state's primary next Tuesday.
The poll by the highly respected Marquette University Law School shows Cruz with the support of 40 percent of likely Republican voters in the state, compared to 30 percent for Trump and 21 percent for John Kasich.
That's a significant swing in the race from the previous Marquette poll in mid-February, which showed Trump up 30 percent to Cruz's 19 percent and Kasich's eight percent.
On the Democratic side, it's a close race between Bernie Sanders at 49 percent and Hillary Clinton at 45 percent, within the margin of error.
In February, it was Sanders with 44 percent and Clinton with 43 percent.
Despite Cruz's lead, a majority of Republican primary voters believe that Trump will secure the GOP nomination. Almost two thirds -- 65 percent -- say they think Trump will win the nod, while 23% say Cruz will be the nominee and just five percent say the honors will go to Kasich.
An even greater share — 77 percent — of Democratic voters believe Clinton will ultimately be the party's nominee in the fall.
The survey of 1,405 registered voters was taken March 24 to 28. The margin of error for Democratic results is +/-6.3 points. The margin of error for Republican results is +/-5.8 percentage points.
This article first appeared on NBCNews.com.