Wisconsin Democratic Rep. Tammy Baldwin became the first openly gay U.S. senator on Tuesday, defeating popular former Gov. Tommy Thompson.

The Senate race was the most expensive in state history with the two candidates raising at least $65 million, Reuters reported.

Baldwin will take the seat of Democratic Sen. Herb Kohl, who is retiring after his fourth term.

Baldwin, 50, is a former Wisconsin assemblywoman who was first elected to Congress in 1998. With her projected victory, she also becomes the first female senator from Wisconsin.

Read it at NBC News.