Thompson had long led in the polls, but has problems with his conservative bona fides: He is on record as having supported a national healthcare plan with an individual mandate, the centerpiece of Democrats' healthcare reform law, and while he opposed the law he worked early on with former Sen. Tom Daschle (D-S.D.) to craft a bipartisan framework. He also increased public employee pensions during his time as governor.

The primary is just a few weeks away, on Aug. 8. If Hovde can maintain his trajectory, he'll be the odds-on favorite, although if deep-pocketed conservative groups backing Neumann, like the Club for Growth and Senate Conservatives Fund, go on the attack against both Thompson and Hovde the field could once again muddle in a hurry.

The winner of the primary will face Rep. Tammy BaldwinTammy Suzanne BaldwinTrade wars and the over-valued dollar Overnight Health Care: Senate panel advances drug pricing bill amid GOP blowback | House panel grills Juul executives | Trump gives boost to state drug import plans | Officials say new migrant kids' shelter to remain open but empty Senators vow to bring transparency to drug pricing MORE (D-Wis.). PPP's poll shows both Thompson and Hovde in a statistical tie with her.

PPP polled 1,057 Wisconsin voters, with an an oversample of 564 usual Republican primary voters, from July 5-8. The primary poll had a margin of error of plus or minus 4.1 percentage points, while the general election polls' margin of error is plus or minus 3 percentage points.