Mayor Bloomberg’s sometimes difficult relationship with his fellow Republicans may come back to haunt him tomorrow night when the Queens County GOP organization is expected to endorse a former City Council minority leader, Thomas Ognibene, over the mayor in a Republican primary.

While the Queens organization won’t make the vote official until tomorrow, sources close to the party said Mr. Ognibene, the Queens GOP vice chairman, has the votes he needs to get the party’s nod. Mr. Bloomberg made calls to Queens leaders over the weekend to win their support, but it is unclear whether he was successful, people close to the discussion said.

If Mr. Ognibene wins the endorsement, it could add momentum to his fledgling campaign and spur Grand Old Party chiefs around the city to defect to the Ognibene camp.

“The mayor is making a heavy effort to get votes,” Mr. Ognibene told The New York Sun in an interview. “I don’t want to predict anything before the vote, but I think they see that Mr. Bloomberg doesn’t represent their interests. Republicans haven’t heard from the mayor for three-and-a-half years and a lot of people are aggravated about that.”

Sources familiar with the discussions among the county leaders in Queens, Brooklyn, and the Bronx said Mr. Ognibene has gained traction among rank-and-file Republicans in the wake of Mr. Bloomberg’s declaration of support for gay marriage, his decision to raise property taxes 18.5% two years ago, and his fundraising efforts for high-profile local Democrats.

People familiar with the discussions among GOP county executive committee members in Queens and the Bronx said both organizations are leaning toward Mr. Ognibene. Brooklyn’s GOP organization is on the fence, three officials privy to the discussions, who declined to be further identified, said.

“Tom’s candidacy is a reflection of dissatisfaction with Bloomberg among the rank and file,” the current minority leader of the council, James Oddo of Staten Island, told the Sun. “When the mayor says I am pro-choice, gay rights, and gun control, the rank-and-file Republicans are going to bristle at that. That heat is going to be felt by the county chairs.”

Mr. Oddo predicted that if Queens threw its weight behind Mr. Ognibene, it would add credibility to his campaign and make Republicans in other boroughs wonder why they, too, weren’t standing up. Queens is the borough where Mr. Bloomberg won the most votes in 2001 – 196,241 on the Republican line and 14,191 on the Independence Party line, out of 390,500 votes cast.

Analysts said a Queens endorsement could help Mr. Ognibene raise the campaign contributions he needs – $250,000 – to qualify for the city’s 6-to-1 matching funds. Support from party organizations also makes it easier to meet the city’s arduous petition requirements.

“The Queens endorsement could snowball,” Mr. Oddo said. “This candidacy is going to be genuine, and they are just beginning to realize that at the other end of City Hall.”

Analysts said the problem is that in the past three-plus years Mr. Bloomberg has done little to give Republicans a stake in his re-election. There are few patronage jobs. Mr. Bloomberg has not gone out of his way to allow Republicans to share in the glory of outer-borough projects he has championed. And Mr. Bloomberg’s relations with Republicans in the council have been frosty at best.

Said one county leader, who did not want to be further identified: “He has given us absolutely nothing, so we have absolutely nothing to lose if we back Ognibene. You can’t make up for three years of neglect in two weeks of calls.”

The case Mr. Bloomberg made to county Republican leaders over the weekend was that the choice wasn’t between Mr. Ognibene and Mr. Bloomberg, but rather between a Republican mayor who has been good for the city and a Democrat who would not be. Mr. Ognibene, the mayor is said to have stressed, wouldn’t be able to best his Democratic challengers in a general election.

“Ognibene has no more chance of being mayor of the city of New York than Ralph Nader would have had to be president of the United States,” Mr. Bloomberg’s campaign manager, Kevin Sheekey, said in an interview. “The Republican leaders have to decide between Mike Bloomberg and the five Democrats who are running against him. That’s the choice they are making.”

A veteran political consultant, Hank Sheinkopf, agreed. He expects that in the end Mr. Bloomberg will win the GOP nomination, not because he will woo Republicans to his side so much as because they will decide it is better to have a Republican mayor in office than to be locked out of City Hall.

“No party likes to be out of power,” Mr. Sheinkopf said. “Republicans are in terrible shape statewide, and in the end the rank-and-file won’t see the point in making it more difficult for a Republican mayor to get elected.”

Still, analysts said there is a lesson for the mayor in the grumbling coming from his right. Even if he does win the GOP nomination, he can’t count on Republicans to support him just because he is running on their party line.

“There is a certain arrogance among people in the administration that Staten Island, for example would never turn to Freddy Ferrer,” a Baruch College professor of political science, Douglas Muzzio, said. “Some of them think Staten Island will vote reflexively for a Republican. That just isn’t true. Freddy can still make Staten Island a battleground, and the administration has to take that seriously.”

Mr. Ognibene, for his part, has been testing campaign slogans in the run-up to his formal announcement for mayor, which could occur as early as next week. His favorite: “After four years, it is time for a Republican mayor again.”