Republican presidential candidate Ted CruzTed Cruz'Never Trump' group ad compares Trump to Reagan Anti-Trump delegates pitch convention rule change to RNC GOP senators: Brexit vote a wake-up call MORE has opened a 10-point lead over rival Donald TrumpDonald TrumpPro-Clinton super PAC to spend .5M in Pennsylvania Sanders: We are working with Clinton campaign 'Never Trump' group ad compares Trump to Reagan MORE in Wisconsin, according to a new poll released Wednesday.
Cruz has 40 percent support, with Trump at 30 percent, the Marquette Law School poll found. John Kasich followed with 21 percent.
The Texas senator's lead comes just days before Wisconsin's primary next Tuesday.
Cruz was seen as slightly ahead in the state before Wednesday's poll. He had led Trump by less than a percentage point in a RealClearPolitics average of polls.
Trump led a February version of the same poll with 30 percent. Cruz had 19 percent and Kasich 8 percent; the candidates who have since dropped out totaled 31 percent at the time.
The poll surveyed 471 likely Republicans voters from March 24-28. Its margin of error is 5.8 percent.