ALBANY – A son-in-law of Richard Nixon, Edward Cox, will establish an exploratory committee within days toward a campaign for the Republican nomination to run against Senator Clinton next year, an aide to Mr. Cox said yesterday.

I. Lynn Mueller, a longtime friend and top adviser to Mr. Cox, said the Manhattan lawyer is ready to take the next step in a possible campaign against New York’s junior senator after four months of informal consideration and meetings with Republican Party leaders.

Mr. Cox opened a bank account in January aimed at raising funds for a potential race against Mrs. Clinton but was limited by election law from soliciting substantial sums or conducting polls, Mr. Mueller said. By establishing an official exploratory committee, Friends of Ed Cox Inc., with the Federal Election Commission some time over the next seven to 10 days, Mr. Mueller said, Mr. Cox will be free to conduct polls and raise money at will.

“Lots of people have been very encouraging based on his resume and his volunteer activities over the last 20 years and based on the fact that he is a very credible individual who could run a very serious campaign for U.S. Senate,” Mr. Mueller said. “Everybody thinks the world of Ed Cox.”

Mr. Mueller said Mr. Cox has retained a Texas-based direct-mail firm, Olsen & Shuvalov, which was once owned by the top political adviser to President Bush, Karl Rove. Mr. Cox also has retained a top fund-raiser for Republicans in the state, Cathy Blaney, his aide said. A first formal fund-raising event for Mr. Cox is scheduled for June 27 at the Fort Orange Club in Albany.

The ability of Mr. Cox to raise money will be essential in a race that is expected to cost Mrs. Clinton and her opponent tens of millions of dollars each. A former congressman, Rick Lazio, spent more than $40 million running against Mrs. Clinton over a period of just six months after Mayor Giuliani dropped out of the 2000 Senate race, citing health reasons. Mr. Lazio lost by 12 percentage points.

Mr. Mueller said he expects a Senate race against Mrs. Clinton will cost her Republican opponent between $50 million and $60 million.

Mr. Cox, 58, married Tricia Nixon, the then-president’s older daughter, in 1971. Mr. Mueller said Mr. Cox, a partner in the firm Patterson, Belknap, Webb & Tyler, took a partial leave of absence from the firm last month and has already spent some of his own money on his early campaign efforts. The aide would not say how much money and said he does not know how much personal wealth Mr. Cox has.

Mr. Mueller said he disagrees, however, with the notion that candidates for statewide office must spend their own money to win.

“Personally and historically, I disagree with the opinion that candidates have to put a lot of their own money into races,” Mr. Mueller said. “That never used to be the standard. I don’t think George Pataki put personal money into his first run for governor.”

The chairman of the state Republican Party, Stephen Minarik, has said he is interested in candidates for statewide office who could pick up some of the tab themselves.

Yet in a meeting with The New York Sun at state Republican headquarters in Albany yesterday, Mr. Minarik suggested that a race against Mrs. Clinton would probably require less personal money because of the personal animosity many voters are thought to feel toward her.

“The key thing is, we are going to find the best possible candidate who will be, I would assume, will be well financed,” Mr. Minarik said. “I will tell you, though, Hillary Clinton is probably, next to Eliot Spitzer, the best fund-raiser we have for the Republican Party in the state of New York. Look what Rick Lazio did in four or five months. Imagine a year’s worth of a campaign.” Attorney General Spitzer is next year’s likely Democratic gubernatorial nominee.

State Republicans are currently engaged in two separate money-raising efforts based largely on antipathy toward Mrs. Clinton.

Despite the prospect of a strong cash infusion from opponents of Mrs. Clinton, a race by Mr. Cox against the former first lady would probably not be acrimonious.

Mr. Mueller said Mr. Cox “has no bitterness toward Mrs. Clinton” and would be motivated by simple disagreement on the issues.

“We just disagree with her, and Ed thinks he can do a better job,” Mr. Mueller said.

The executive director for the state Democratic Committee, Rodney Capel, said the appearance of Mr. Cox as a potential Republican nominee suggests the party has done a poor job of cultivating candidates to run against Mrs. Clinton.

“I don’t have much to information on him to go on other than the connection to the name Nixon,” Mr. Capel said. “I don’t think they have a very deep bench.”