Connecticut Republicans are facing their first contentious battle for a Senate nomination in more than 15 years, but it’s not clear whether spending big bucks now ­— as some candidates are doing ­— will help in the long run.

With about 1,600 GOP delegates poised to pick the party’s nominee at their annual convention in May, this could be one contest in which spending heavily on television ads has diminished returns.

Five Republicans have lined up to run for the chance to challenge Sen. Chris Dodd (D-Conn.), one of the most vulnerable Senators up in 2010. Former Rep. Rob Simmons was viewed as the early establishment frontrunner, but since then at least two of the candidates have demonstrated that they are willing to fund their own campaigns to varying degrees. That means it’s even more likely the Republican fight will be carried on to an Aug. 10 primary — three months after the party faithful select their desired nominee.

According to state GOP Chairman Chris Healy, the task is for candidates to court and persuade as many of the 1,600 delegates from the 169 Republican town committees as possible until the May 21 convention.

“It is a challenge, but we’re a small enough state and these committees are small enough and they’re cohesive enough that they do it by meeting with town committees in their regular meetings,— Healy said.

Connecticut Republicans have not had a competitive primary for a statewide office since 1994, when then-state Sen. Jerry Labriola defeated another Republican at the convention to win the Senate nomination and then defeated the same Republican a few months later in the primary. The competition to be a delegate to the convention has been scarce in more recent years, but that will not be the case this cycle with the crowded field seeking the GOP nomination.

“I can guarantee you that this will be one state convention that will be well-attended,— Healy said. “And that will be exciting.—

A candidate must secure 50 percent plus one of the delegates’ support to win the nomination and receive top billing on the August ballot. But any candidate who passes a predetermined threshold, usually 15 percent of the vote, will also be listed on the ballot. If candidates do not reach the threshold, they can petition to get on the ballot by collecting signatures ­— an arduous and expensive process.

Former World Wrestling Entertainment CEO Linda McMahon has already given her campaign $3.5 million and has told Republican officials that she is willing to spend up to $50 million in her bid against Dodd. She started her campaign by spending millions on television ads in Connecticut and in the New York City media market.

“I launched this campaign with a significant media buy because no one in the state really knows who I am, and I think that’s really important,— McMahon said in a phone interview.

But as a first-time candidate, McMahon also has a challenge courting the 1,600 delegates and superdelegates headed to the May convention. Like the other candidates in the race, McMahon is spending significant time talking to local party officials who will either be convention delegates or pick the delegates next year.

“Since I announced in mid-September, I’ve done over 100 events,— McMahon said. “I’m having individual meetings with [Republican town committee] chairmen and further meetings with the town committee.—

McMahon declined to say whether she would drop out of the contest if she did not win the Senate nomination at the convention or if she would continue to pursue a bid if she got enough support to get on the ballot without the nomination. Even if she didn’t have enough support at the convention, McMahon would have the funds to support a petition drive to get on the ballot.

One Connecticut Republican criticized McMahon’s strategy of spending so much money early in the race.

“There’s no doubt that she’s brought an elephant gun to a mouse fight,— the Republican said. “Is it a waste? No. Is it overkill? Yes.—

The Republican also said McMahon could clear the field if she has a strong showing at the convention.

“If she were to win the convention, the race for the nomination would be over at this point,— the Republican said.

To make matters even more complicated, the vast majority of delegates to the convention have not been selected yet. Republican town committee chairmen, who typically oversee the delegate selection process, are up for re-election in early 2010, and delegates will be chosen soon after that. Although many delegates are repeat customers and well-known GOP activists, the uncertainty of the final delegate pool poses a problem for candidates looking to court their votes.

Simmons, a former state legislator and three-term Member of Congress, arguably starts out with an advantage in the delegate contest because he knows many of the activists. He told Roll Call in an interview in September that he would not force a primary if he did not win the nomination at the convention ­— a statement that his campaign confirmed this week is still valid.

“I have announced that if I don’t win the convention, I will not engage in a primary for a simple reason that our Republican Party here in Connecticut is a minority party,— Simmons said in September. “When a minority party engages in a primary, it can be very divisive and undercut our efforts in the general election.—

In Congress, Simmons represented much of eastern Connecticut, and his challenge now is to court voters in the western part of the state, including Fairfield County.

“He is working his tail off aggressively reaching out to delegates, likely delegates and people who will be influencing the delegate selection process,— Simmons campaign manager Jim Barnett said.

Former Ambassador to Ireland Tom Foley is the other candidate besides McMahon who has already hit the TV airwaves with ads, pumping $539,000 of his own funds into his bid so far. He said most Republicans he meets with have seen his spots.

“Name awareness is important,— Foley said. “It’s certainly going to be important next summer, assuming there’s going to be a primary. It doesn’t hurt to build that base now.—

He said he’ll run in the primary if he qualifies for the ballot, even if he does not win the nomination. He said he does not plan to run if he cannot meet the delegate threshold to get on the ballot.

“I think with the delegates, you’re trying to have them get to know you, what your positions are on the issues,— Foley said. “They’re more process-focused than the typical voter. They want to know how you’re going to win, why you’re the best candidate.—

As a delegate to the 1994 convention, state Sen. Sam Caligiuri remembers the last time Republicans had a real fight for the nomination. Now that he’s a Senate candidate, he’s traveling to visit the local town committees to talk to potential delegates and chairmen.

“Hopefully they’re predisposed to supporting you when they select delegates at the convention,— Caligiuri said.

If he doesn’t make the ballot at the convention, Caligiuri said, he won’t petition to get on the ballot in September. But if he loses the nomination and still qualifies for the ballot, he’ll have to wait and see, he said.

“It’s going to depend on a lot of factors: Who else is in the race? How far beyond the 15 percent that I have? Will I have the financial resources?— Caligiuri said.

A campaign spokesman for businessman Peter Schiff (R), who is also running, did not return a request for an interview.