Wisconsin Democratic Rep. Mark Pocan is endorsing Bernie Sanders for president, giving the Vermont senator a boost in the battleground state three months before its primary.

Pocan didn't endorse anyone in the 2016 primary.

"For three years now, Donald Trump has poisoned our nation with his failure, corruption, and xenophobia," Pocan said according to the Sanders campaign. "Bernie Sanders’ authenticity, honesty, and movement for equality is the antidote our nation needs now. I am proud to endorse a candidate that shares my progressive values and has long been an advocate for the issues Wisconsinites care most about."

Sanders and Massachusetts Sen. Elizabeth Warren have been battling to win over the liberal wing of the Democratic Party.

Pocan's endorsement is a big score for Sanders in Wisconsin. Sanders won Wisconsin by 13 points in 2016.

"I’m so proud that Rep. Pocan is supporting our movement and will chair our campaign in Wisconsin," Sanders said. "Mark Pocan is a champion of workers rights and has always stood up to the horrible corporate trade deals that have outsourced millions of jobs. Donald Trump lied to workers in 2016 and then betrayed them as president. With Mark’s help, we will win Wisconsin in 2020 and defeat Donald Trump."

The latest Marquette Law School Poll released Wednesday found the top four democratic candidates among primary voters to be former Vice President Joe Biden, Pete Buttigieg, Sanders, and Warren.

The poll found Biden to be leading the Democratic Primary candidates at 23 percent, followed by Sanders at 19 percent.