Leah Vukmir won her primary for U.S. Senate in Wisconsin, a state that has never had a female Republican senator. She'll face Democratic Sen. Tammy Baldwin in the November general election.

Why it matters: Baldwin is one of 10 vulnerable Democratic senators this cycle because she's a Democrat in a red state. At least four billionaires in the state have pledged to back the Republican nominee, which will give Vukmir a huge boost in November.