AUGUSTA — Lewiston is a Democratic town. That has been the conventional political wisdom — and reality — for decades.

It’s also the message that has been received by GOP candidates looking to get elected to the Maine Legislature from Maine’s second-largest city.

But Republican Party leaders are planning to wage a high-profile campaign in the city this year. They’re optimistic that with the retirement of popular incumbent Democratic senator Margaret Craven and a well-known candidate from the business community on the GOP ticket, they just might swing the district, which represents all of Lewiston.

Patricia Gagne, an Allstate insurance agent and chairwoman of the Androscoggin County Chamber of Commerce, is the only announced Republican candidate for Senate District 21, which replaces Senate District 16 as part of this year’s legislative redistricting. Gagne is a lifelong Lewiston resident with ties to the business community, factors that Republicans hope will help flip a longtime Democratic district for the first time in decades.

Last week, a day after Craven announced her retirement from the Senate, Rep. Nathan Libby, D-Lewiston, announced that he’d run for the Senate seat. Libby is a Bates College graduate, Lewiston city councilor and consultant.

“Nate is a very strong campaigner. He’ll work hard. But we probably have the strongest candidate we’ve had in a long time,” said Stavros Mendros, chairman of the Androscoggin County Republicans. “She’s [chairwoman] of the chamber, she’s Franco. People know her and love her. … She’s not a sacrificial lamb, like they’ve been in the past.”

Mendros, for what it’s worth, said he was one of those sacrificial lambs: He ran against then-Sen. Peggy Rotundo in the district in 2004 and garnered fewer than half the votes she did.

That result is indicative of Lewiston’s recent past; the city has been relatively easy pickings for Democrats for decades. In 2013, registered Democrats and unenrolled voters each outnumbered registered Republicans by more than two to one. The city hasn’t elected a Republican to the state Senate going at least as far back as 1968, when the state stopped electing senators on an at-large basis by county.

In the House, there hasn’t been a Republican representative from a Lewiston-only district since Mendros was last elected to District 88 in 2000. Even then, he was the only Republican lawmaker from the city. Before Mendros, it had been 15 years since a Republican was elected to a Lewiston-only House district. That year, five Democrats also represented the city in the House.

Republicans in other elections have had better luck in recent years. While Lewiston has always gone for Democrat Mike Michaud in Congress, the city went for Republican Sens. Susan Collins and Olympia Snowe every time they ran. In 2010, Republican Gov. Paul LePage — a Lewiston native — won the city, and the city elected conservative mayor Bob Macdonald in a low-turnout race in 2011, and while city elections are technically nonpartisan, fiscal conservatives outnumber liberals on the city council.

Lewiston voters are “ticket splitters, they’ve shown that in the past,” said state GOP Chairman Rick Bennett. “It’s still Democratic terrain, but it’s increasingly competitive.”

Gagne said she believes Lewiston residents are more willing to vote for Republicans than they have been in the past, but said she’s not playing up her party affiliation, though she is campaigning on welfare reform and lower taxes — two top GOP issues.

She touted her community involvement as a lifetime resident of the city — Libby moved to Lewiston to attend Bates, where he graduated in 2007, and has stayed there ever since. She’s in the local Kiwanis Club, volunteers in different charitable groups, attends Mass every morning and is a youth pastor, she said. That transcends party lines, she said.

“I think I’ve been very visible, which I think is a big help for me, being accepted by a lot of people,” she said. “When people see Patti Gagne, they don’t see a Republican, they see a person who cares.”

On paper, Gagne has a few advantages over Libby: She’s privately financing her campaign, meaning she could spend far more than Libby, who will be publicly financed. Plus, LePage is on the gubernatorial ballot again in 2014, which could drum up support for Gagne, but Michaud, his Democratic opponent, has also been hugely popular in the city, which could negate the so-called “LePage effect.”

Libby, on the other hand, has the support of Craven, who has been immensely popular in the city. He’s also widely regarded as an effective campaigner, and will likely have the backing of the liberal Maine People’s Alliance, a powerful group for which he used to work.

Ben Grant, chairman of the Maine Democratic Party, said the enthusiasm and optimism by Republicans in Lewiston isn’t anything new — which is telling, he said.

“We’re not taking anything for granted, but Sen. Craven won her last race by almost 6,000 votes,” he said. “We’ve been hearing this for as long as I’ve been here, that the other side is going to make Lewiston a real focal point, but it hasn’t materialized in any real competitive races.”

Grant said the idea that Lewiston voters would favor a candidate because they were born in the city or have a French last name is an insult to those voters, and belies the truth of successes by people such as Craven and Rotundo, who are neither native Lewistonians or French-Canadian.

“I respect the voters of Lewiston, and I think they vote for people they know will serve them well,” he said. “Democrats support the city of Lewiston better than Republicans do, and that’s why they keep winning.”

Libby said voters in his city “vote for the person, not the party,” and said his political experience make him the best Senate candidate in the race.

“A lot of legislative issues have a direct impact on the city of Lewiston,” he said. “I have experience in the Legislature as well as the city council, and that’s very important if you’re serving in the state Senate. I think a state senator from Lewiston needs to hit the ground running.”

As for Craven, the outgoing six-term lawmaker, who has served on the Legislature’s budget-writing Appropriations Committee and currently chairs the Health and Human Services Committee, said LIbby should do well in the election.

“Any Democrat worth their salt should be able to win in Lewiston,” she said.