- Cruz and Sanders are the leaders in Wisconsin ahead of the state's primaries
- Kasich and Sanders are the two best-performing candidates in the general election
Cruz, the Texas senator, tops the Republican field with 40% support, compared to Trump's 30% and Ohio Gov. John Kasich's 21%.
Sanders, meanwhile, has 49% backing to Clinton's 45% in the Democratic race.
The 2016 presidential campaign has descended on Wisconsin ahead of the state's April 5 contest. It's the only major primary before New York's two weeks later, and is seen as a gauge of momentum for the GOP establishment's anti-Trump efforts.
The poll also showed that Sanders beats all Republican candidates in head-to-head matchups in the Badger State. He topped Kasich, 46% to 44%, and crushed Cruz, 52% to 29%, and Trump, 54% to 35%.
Kasich easily bested Clinton head-to-head, with 48% support to her 39%. Clinton and Cruz tied with 44% apiece. And Clinton easily beat Trump, 47% to 37%.
Those numbers could offer ammunition to both Sanders and Kasich, who have argued that polls show them as their parties' most electable candidates. And they could help Cruz make the case that Trump would lose to Clinton -- though the results show weakness for him, too.
The survey was conducted March 24-28, before CNN's Republican town hall on Tuesday night in Milwaukee. The margin of error on the Republican side is plus or minus 5.8 percentage points; with the Democrats, it's 6.3 points.