Sen. Thomas R. Carper is the latest longtime Democrat facing a competitive primary, but he insists he won’t be caught by surprise.

Carper is universally known in Delaware, having served in the House and then as governor before arriving in the Senate in 2001.

But Kerri Evelyn Harris, a 38-year old community activist and organizer from Kent County, who is (like Carper) a military veteran, has gained support from progressives, especially in the aftermath of the victory of Alexandria Ocasio-Cortez in the House primary in New York against House Democratic Caucus Chairman Joseph Crowley.

On Tuesday, the insurgents claimed another veteran when Rep. Michael Capuano, D-Mass., lost in the Democratic primary to Boston City Councilor Ayanna Pressley.

With that Massachusetts primary in the rear-view mirror, Harris is the next challenger in the spotlight.

“[Carper] has definitely become a corporatist,” Harris said in Dover, according to the Associated Press. “His entire career, if you look at it, has been centered around making sure corporations thrive, and almost a Republican idea of there will be a trickle-down effect. We know that trickle down doesn’t work.”

Delaware is a largely Democratic state, though its favorable business laws have led many financial institutions and other corporations to set up shop there.

There’s precedent in Delaware for a political outsider unexpectedly winning a party primary. Former House member and Gov. Michael Castle, a Republican, was the favorite to win the Senate seat vacated when Joseph R. Biden, Jr., left to become vice president.

“Mike Castle’s a very close personal friend,” Carper told reporters at the Capitol in August. “He and I ride down on a train together probably every other week. And I asked him months ago, when it looked like I was going to have a primary — I’ve had primaries before for Congress and for governor — and I asked him how did you get beaten by Christine O’Donnell?”

O’Donnell was the tea party-backed Republican who was ultimately trounced in the general election by Democrat Chris Coons, who still holds the Senate seat. At one point in the campaign, after reports surfaced of O’Donnell’s interest in pursuing witchcraft, she went on the air with an ad, speaking into the camera the words that would define the race: “I am not a witch.” Coons ran away with the race, winning 57-40 percent. 

Carper said Castle told him that they didn’t run much of a get-out-the-vote effort in that GOP primary.

“Everybody stayed home. They said nobody would beat Mike Castle. That’s what they thought,” Carper said.

In contrast, the Democratic incumbent said he was continuing to rack up the miles on his Chrysler Town & Country minivan — a bit of a staple of Carper’s political campaigns.

“I always campaign as if my opponents are 10-feet tall,” he said. “I always campaign like I’m 20 points behind, and so at the end of the day they won’t be 10-feet tall and I won’t be 20-points behind.”

Carper has been upbeat about his own poll numbers in the race against Harris, but the fact that Biden actually jumped in with an endorsement in late August, as reported by NBC News, highlighted that it could be a real race.

The progressive group Justice Democrats, which is among the organizations backing the Harris challenge, criticized the Biden endorsement.

“Biden’s endorsement of Carper is about protecting the corporate class and big donor interests,” the Justice Democrats said on Twitter. “Kerri Harris is the ONLY candidate committed to fighting inequality by putting regular people before the corporate class.”