ALBANY – A conflict has erupted in state Republican circles over next year’s U.S. Senate race, with one potential opponent of Senator Clinton accusing party leadership of picking a favorite long before challengers have had a chance to generate grassroots support.

A spokesman for Manhattan lawyer Edward Cox, a son-in-law of Richard Nixon who recently set up an exploratory committee for a possible run against Mrs. Clinton, said the state Republican chairman, Stephen Minarik, and the executive director of the state GOP committee, Ryan Moses, threaten to derail Mr. Cox’s efforts by signaling that Westchester County’s district attorney, Jeanine Pirro, is the best candidate for the job.

“As recently as last week we told Steve Minarik and Ryan Moses that we didn’t appreciate their saying they back Jeanine Pirro, and the answer was, ‘We’re not backing anybody,'” a top strategist for Mr. Cox, I. Lynn Mueller, said. “I responded that the only two people in town who don’t think you’re supporting Jeanine Pirro is you two.”

Ms. Pirro announced last month that she plans to seek statewide office next year, but she declined to say whether that office would be governor, attorney general, or U.S. senator. Republican sources said that party leaders, including Mr. Minarik, are urging Ms. Pirro to run against Mrs. Clinton and that she has recently begun to express interest in the race.

Mr. Moses did not deny that his boss has a personal favorite in next year’s election. But he said that would not have a chilling effect on the other candidates’ ability to generate support. Mr. Moses said Mr. Minarik has encouraged Mr. Cox to tour the state and to raise money for a possible campaign and would continue to encourage him.

“While Steve may support Jeanine Pirro personally, he has encouraged all potential statewide candidates to get out and meet with the state committee and county chairs who are the decision makers in this process,” Mr. Moses said.

Republican candidates for statewide office will be chosen at a party convention next year. Two representatives from all 150 Assembly districts will cast a vote, with votes weighted by a county’s Republican strength in the last gubernatorial election. Candidates need 25% of the vote to qualify automatically for a party primary.

Mr. Mueller conceded that Mr. Minarik has helped arrange appearances around the state. But he said Mr. Minarik’s private efforts at securing a Pirro candidacy are aimed at freezing out other candidates.

“I’m sitting here waiting with bated breath because we’re supposed to wait until she makes a decision,” Mr. Mueller said. “I believe it’s inappropriate for the state chairman to choose sides when you have an open seat and you have at least two qualified candidates out there, and one with an exploratory committee and another who has been flirting with the notion.”

Some state Republican leaders have been forthright in endorsing Ms. Pirro ahead of her announced intentions. The Erie County party chairman, Robert Davis, said it would be wise for Republicans to get behind a candidate early so as to avoid the kind of defeat a former congressman, Rick Lazio, suffered in his 2000 race against Mrs. Clinton after a late entrance.

“I think we can beat Hillary Clinton, but primaries deplete resources from the standpoint of manpower and finances,” Mr. Davis said. “… We can’t afford to be divided, and primaries are divisive.”