The crowd packed itself thick in a grimy bar in New Orleans last week. A folk and blues band was playing its songs, beloved among the city’s downriver hipster set. But the real star of the show was an aging cattle farmer from conservative northern Louisiana.

His name, which few people in the crowd knew before this year, is Foster Campbell. In a run-off election next month, he will vie for the last open U.S. Senate seat. He is a longshot—but if he can defy the latest public poll, he might also be the Democratic Party’s last best hope of slowing down Donald Trump.

Although Republicans secured control of the Senate on election night, the institution’s rules still give considerable power to the minority party. If Democrats control 49 seats instead of 48, they will be that much closer to peeling off Republicans to stop some of Trump’s most controversial agenda items.

Or as Campbell puts it, “I might be the deciding vote on privatizing Social Security, privatizing Medicare. One vote can make a difference in the Senate.”

As Republicans prepare to to take over the presidency and both chambers of Congress for the first time since 2007, out-of-state liberals are paying attention to Campbell. Last week he appeared on Rachel Maddow’s show, and a Medium post about his campaign, called “The 2016 Election Isn’t Over Yet,” has been shared hundreds of times. Campbell says he has seen a surge in out-of-state donations since Nov. 8, although he declined to provide an exact figure.