For the first time in 18 years, incumbent Congressman John Tierney will not be on the ballot after losing the Democratic primary last month.

  Now the North Shore's 6th District has been turned upside down.

“Serving in Congress, representing this district for the last 18 years has been the greatest privilege and honor of my life,” Tierney told supporters in his concession speech last month.

That made Tierney’s second place finish the greatest political loss of his life. Which left voters, well, a little disoriented …

“Well, honestly, I’ve been a Tierney supporter for quite a while," one resident of the 6th said, laughing. "And so it’s a tough change for me. At the same time, it goes back to having a new perspective, especially after 18 years.”

Regardless of who wins, the 6th district will be represented with a new perspective. Republican state lawmaker Richard Tisei is openly gay. Democrat Seth Moulton is an Iraq war vet. They want to blur party lines to appeal to undecided and independent voters.

“We’re getting out and meeting as many voters as we can,”

Moulton said. He's trying to unite the Democratic base after a hard-fought primary victory over Tierney.

“There’s a tremendous amount of enthusiasm and excitement in the district," Moulton said. "I was talking with the fishermen up in Gloucester and they appreciated the fact that I came and listened.”

Moulton is a Harvard grad and Marine vet. He speaks most passionately about his time in Iraq, where he served four tours of duty.

“Now that we all know that there are chemical weapons in Iraq, there has to be a full accounting of them,” he said at a legion hall in Lynn.

And he talks openly about receiving treatment now that he's home.

“I get my healthcare from the VA," he said. "I actually have a doctor who’s very dedicated to his job. But he’ll send me down the hall to get my blood drawn and I can wait in line for 2 hours. Or he’ll refer me to another doctor and I can wait months to get an appointment.”

What Moulton accomplished in his primary victory, Tisei nearly accomplished two years ago, in a hard-fought, bitter and one-percentage-point loss to Tierney. Now Tisei is using Tierney’s defeat to pick off disgruntled Democratic voters.

“I was in a very close race two years ago and I learned that every community, every region of the district is extremely important," Tisei said. "I expect this to be another close race this time around and I don’t want to leave any stone unturned.”

Tisei calls himself a champion of small business — he’s a ubiquitous figure on main streets in his district. Over black coffee at Brothers Deli in his hometown of Wakefield, he hears anxiety about the future.

“Right now whether it’s Ebola, ISIS, the economy, the incompetence of government in general, whether it’s the VA, the IRS, the Secret Service — people are really concerned,” he said.

Tisei’s determination is inspiring some people to cross party lines. Democrat Marisa DeFranco, who took on Elizabeth Warren and lost to Moulton in the primary, is now supporting Tisei.

“All that I know about Richard, he’s a common sense Republican," DeFranco said. "He fights his party on some very core issues, and that’s what I’ve been trying to do for the last several years and that really shows testament to somebody’s character.”

Tisei’s support is also coming from some in the gay community, which traditionally supports Democrats.

“We feel that if the only reason you wouldn’t vote for Richard Tisei is because he’s a Republican, he’s worth another look,” said Sue O’Connell, co-publisher of Bay Windows newspaper, New England's largest publication for the LGBT community.

“Richard Tisei is openly gay, he’s a moderate Republican," she said. "He has done a lot of hard work for the LGBT community as a state representative. So he’s got a proven track record.”

But to reinforce how divided the district is, the state’s most prominent gay politician, former U.S. Rep. Barney Frank, is voting the party line.

“I was in support of John Tierney, but Seth Moulton is right on the issues," Frank said. "He’s intelligent."

Frank says Moulton has to go to Washington, because no Republican from Massachusetts can make a difference while John Boehner is Speaker.

“The Republican Party’s control of the House clearly means that nothing that I care about is going to get advanced, including LGBT rights," he said. "You’ve got a very conservative control of the Republican Party, and it really, unfortunately, doesn’t matter what some individual Republicans say."

Frank says it’s always important to consider crossing party lines on voting day. But the crisscrossing that’s happening is both confusing and an opportunity for candidates to show their broad appeal.

“Independents hold the cards, no questions about that,” said WGBH News political analyst David Bernstein.

“A lot of them are just Republicans," he said. "Other independents in the district, particularly in the cities, tend to be Democratic voters. Those are the ones that will be very interesting to watch because they are really deciding whether to vote Democrat as they usually do, or are they sold on the right kind of Republican for the job.”

What Moulton and Tisei have in common is that they’ve both taken on a sitting U.S. Representative. But to win the seat, both plan to sharpen their messages to prove that it’s one thing to have challenged Tierney, it’s another to win his seat.