Delaware Democrats go to the polls on Thursday in what has suddenly become a much-anticipated primary matchup between Sen. Tom Carper, who has been serving in public office since 1976, and Kerri Evelyn Harris, a black, LGBT Air Force veteran and community organizer who wasn’t born by that time.

While several insurgent candidates have unexpectedly defeated House incumbents in 2018 primaries — including Ayanna Pressley’s win Tuesday night in Boston against 10-term House incumbent Mike Capuano — unseating an entrenched, establishment-backed, three-term U.S. senator like Carper is a much tougher challenge. From the start, Harris has been, and still, regarded as a clear underdog. But this race has become increasingly compelling.

Harris has waged her campaign by arguing that it is not enough simply to resist President Donald Trump some of the time; the underlying rot that allowed for Trump’s rise must also be addressed. Doing that, she argues, requires politicians to forgo corporate money and instead rely on small donors, volunteers, and robust community support.

Two months ago, Harris barely had a campaign, and she only recently opened her first office. A private poll earlier this month found Carper with a gaping lead and a high approval rating. But even among those polled, support for Carper plummets when his record is poked. That means that Harris has a path to victory, but only if she can get her name and her message out to enough voters in time.

The campaign now has three offices, one in each of Delaware’s counties. It was recently boosted by the independent backing of the Working Families Party, which is spending $100,000 on mail, digital ads, and canvassers. The project is being run by WFP senior political strategist Ari Kamen and Claire Sandberg, an alum of both the Bernie Sanders and Abdul El-Sayed campaigns.