On Friday, Sen. Roger Marshall took a rare step for a Republican incumbent running in Kansas: launching an attack ad against his Democratic rival.

When pastor Adam Hamilton launched his campaign for the seat four months ago, the odds seemed long. The state has not sent a Democrat to the Senate in nearly a century, and President Donald Trump has won it by at least 14 percentage points in all his campaigns.

But as the traditional post-Labor Day sprint to the midterms begins, Hamilton is optimistic.

“People are very frustrated,” Hamilton said in an interview, recalling a recent conversation with a 79-year-old man who handed him a receipt for diesel for his truck and told him, “This is why I’m voting for you.”

From the suburbs of Philadelphia to California’s Central Valley, such stories are fueling Democratic hopes that they can not only flip the House but also capture the majority in the Senate by running strong campaigns in GOP territory. If successful, Democrats would both provide a consequential check on President Donald Trump for his final two years in office and begin to repair their party’s tattered brand as they prepare for the next presidential election.