Four county Republican organizations will endorse Mayor Bloomberg at a press conference in the next few weeks, The New York Sun was told yesterday. The announcement is aimed at leveling a blow at the upstart campaign of Mr. Bloomberg’s Republican challenger Thomas Ognibene, who secured the endorsement of the Queens Republican organization last week.

More than six months before the primary, leaders from the New York County, Kings County, Bronx, and Staten Island Republican organizations will endorse Mr. Bloomberg for his education reforms and steady stewardship of the city’s economy, people close to the discussions told the Sun. Besides Mr. Ognibene, another Republican, an investment banker named Steve Shaw, plans to run against the mayor in the primary.

“The Bloomberg campaign had to do it and had to do it soon because clearly the Queens endorsement frightened them,” a Baruch College professor of political science, Douglas Muzzio, said. “Dr. Johnson said that the prospect of a hanging concentrates the mind wonderfully, and the Queens endorsement was just that: It concentrated Bloomberg’s mind on getting the support of the other four counties.”

For the Bloomberg campaign, rolling out the Republican county leaders in a united front will come just weeks after Mr. Ognibene, vice chairman of the Queens County Republican Party and a former minority leader of the City Council, won the key endorsement of the Queens County GOP. Republican leaders in Queens said they were backing Mr. Ognibene because he represented the Grand Old Party’s values better than Mr. Bloomberg.

In particular, Queens Republicans grumbled about the mayor’s smoking ban, his 18.5% increase in property taxes, and his propensity to distance himself from President Bush and the party as reasons for their decision to back Mr. Bloomberg’s challenger. The announcement focused minds in the Bloomberg campaign because in the general election four years ago, two-thirds of Mr. Bloomberg’s 78,040-vote margin of victory came from Queens.

“Clearly this shows the Bloomberg team is worried about Ognibene, he represents a threat to them, and this is a way to contain that threat,” Mr. Muzzio said.

In a typical year, the county organizations make their endorsement announcements in April with an eye to a May 15 deadline they have to meet to print petitions. In the case of the Manhattan Republican Party, for example, they put the whole slate of endorsed candidates on the voter guides. Mr. Ognibene’s decision to brandish an early Queens endorsement sped up the timetable, party officials said.

The mayor’s loss of the Queens endorsement was followed by a close call. Until last week, the Bronx party’s support was still in play. The holdouts were a very conservative Catholic faction who had been pressing their county leaders to throw their weight behind Mr. Ognibene. While they had many of the same reservations about Mr. Bloomberg’s Republican bona fides as Queens officials had voiced, the Bronx officials were doubly angry about Mr. Bloomberg’s part in sending Bronx Republicans’ longtime power in the state Senate, Guy Velella, back to jail.

A local conditional release board that was appointed by the mayor decided to release Velella from Rikers Island last September, saying the three months he had served of a one-year sentence for bribery conviction sufficed. Mr. Bloomberg, when he learned of the release, forced the entire board to resign and called the whole incident “an outrage.” The mayor eventually won the day. Velella went back to Rikers in December, and Bronx Republican leaders groused that the mayor unnecessarily piled on their fallen comrade.

While the Republican organizations are said to have closed ranks around Mr. Bloomberg, there is still some grumbling behind the scenes, political analysts said. The one thing that keeps coming back is what they portray as the presumptuous view of the Bloomberg campaign that everyone has a price, they said. Whether it is what the mayor’s team, with its deep pockets, really projects, or just what party members perceive, is unclear. They complain further about Mr. Bloomberg’s noticeable absence at club meetings and his disdain for the grassroots schmoozing that usually occurs between candidates and the local party faithful.

“Bloomberg’s campaign team has a sense that whatever is wrong, money can fix it,” one Republican official, who declined to be further identified, said. “I don’t get the feeling that he likes to be around us, either, so he avoids us and then expects us to endorse him just because he is running as a Republican. It is rubbing a lot of people the wrong way.”

For Mr. Bloomberg and his strategists, now that the county Republican organizations have weighed in, the next concern is whether Mr. Ognibene is able to play spoiler by being the odd man out in a three-candidate race in November, running against the mayor and his Democratic opponent on the Conservative Party line. Mr. Ognibene rose through the ranks of the state’s Conservative Party before he became a Republican Party leader.

Two officials familiar with the discussions said the leader of the Conservative Party, Michael Long, has yet to commit to any candidate.