PORTLAND — Jon Courtney didn’t expect to win the 1st District Republican primary by a landslide, but Maine’s Senate majority leader never thought that a relative unknown would pose such a threat to his bid to unseat Democratic U.S. Rep. Chellie Pingree in November.

Patrick Calder, a political newcomer from Portland, conceded the nomination to Courtney during a joint news conference Wednesday afternoon. The announcement followed a neck-and-neck, nail-biting election night that often put Calder slightly ahead of the experienced legislator.

In the end, the vote was razor close — 14,547 to 14,282 — giving Courtney a 265-vote lead representing less than one-tenth of 1 percent of total votes cast.

Courtney admitted that he wanted a stronger endorsement from Republican voters — his campaign had hoped for at least 55 percent of the vote. But he’s pleased to have won the nomination after little more than a month of campaigning. And he’s glad that Calder will be on his side in challenging Pingree.

“I’ve been the dark horse before, so I know all about close races and being the underdog,” said Courtney, 45, who lives in Springvale and operates three dry-cleaning shops.

“But this seat is not an entitlement for me or for the congresswoman,” Courtney said. “It belongs to the people of Maine and I would be honored to serve them in it.”

Calder, 29, is a cruise-ship engineer and is chairman of Portland’s Republican City Committee. This was his second run for public office. In 2010, the Eastport native ran unsuccessfully against Democrat Peter Stuckey in House District 114.

At the news conference at Pat’s Pizza in the Old Port, Calder said he wouldn’t seek a recount, though supporters told him it was his right under state law. Calder said he wanted to avoid the additional cost to taxpayers and offered his “full, unequivocal support” to help Courtney become the next 1st District congressman.

“The results were clear, if close, and I congratulate Sen. Courtney on his victory,” Calder said. “The primary is over. We’re all on the same side now. We have far more that unites us than divides us. We all believe in the freedom of the individual, less government and lower taxes.”

Courtney praised Calder’s gentlemanly concession, effective grass-roots campaign and intelligent, articulate manner. Though Courtney came out ahead in his home district and York County, Calder won more votes across Cumberland, Kennebec, Lincoln, Knox and Sagadahoc counties.

“There’s a lot of people that listened to Patrick Calder,” Courtney said. “Let me tell you, Patrick Calder has a good message, and it’s a message that’s going to be part of our campaign going forward. It’s about uniting. It’s about reaching out to all factions of the party. It’s about reaching out to all people, Republicans, independents and Democrats.”

Courtney and Calder noted the financial challenge of running against Pingree, who already has raised $599,000 and spent $407,000 this election cycle, according to the Federal Election Commission. In contrast, Calder raised $7,557 and spent $6,156, most of it his own money; and Courtney raised $22,381 and spent $5,736, according to the FEC.

“We knew whoever won the primary was going to be the underdog,” Courtney said.

Pingree phoned Courtney Wednesday afternoon to congratulate him and wish him the best during the campaign.

“I’m looking forward to a healthy, positive debate this fall on the important issues that Maine families face,” Pingree said in a news release. “It’s been an honor to serve the people of Maine and I’m working hard to earn another term in Congress.”

Courtney said he will work hard in the coming months to win support across the 1st District, noting that polling has shown that only 25 percent of people in his Senate district know who he is. Courtney has been a legislator for 10 years, including one term as a state representative.

“You can’t get caught up in, ‘I’m the Senate majority leader and everybody should know me,'” Courtney said. “Where I’m known, people know that when I say I’m going to do something, I do it.”

Given the results of this primary, Calder’s supporters said it won’t be long before their candidate is back on a ballot. Kirsten Martin of Portland, who was Calder’s campaign treasurer, described him as a rising star in the Maine Republican Party.

“He’s smart, he knows what he’s talking about and he says it so people can understand,” Martin said. “Being an unknown and only 29 years old, it’s huge for him to have come so far. I think in the future, when the time is right, he should throw his hat back in the ring.”