The Democratic Party of Wisconsin endorsed U.S. Rep. Tammy Baldwin on Monday as the party's nominee for the U.S. Senate seat being vacated by Herb Kohl.

"While the Republican Tea Party field runs further to the right and into the arms of their Wall Street masters, Tammy Baldwin has shown that she will fight these interests and protect our struggling middle class," Democratic Party of Wisconsin Chair Mike Tate said.

Kohl and former Wisconsin Sen. Russ Feingold (D) have also endorsed Baldwin’s candidacy for the Senate.

If Baldwin won, she would be the first openly gay U.S. senator. But she has said she does not want her campaign to revolve around her sexuality.

Baldwin is the only Democrat to have declared her candidacy for the seat. Her Senate campaign raised more than $1.1 million last quarter.

Baldwin will face Tommy Thompson, Mark Neumann, Jeff Fitzgerald or Frank Lasee depending on who wins the Republican primary in August.