Saying he is almost certain to run for governor, Howard County Executive J. Hugh Nichols appointed an "exploration committee" today to test the waters for him.

The committee, which includes many of the state's most prominent Republicans, is not expected to make its report until next year. But Nichols, who switched from the Democratic to the Republican Party earlier this year after failing to build support among Democrats for his gubernatorial campaign, said he is "extremely optimistic" about running. The committee, he said, "is intended more to see if there are any problems" that nobody has anticipated.

Nichols, who cannot run for a third term as county executive, was still being cautious about announcing he will run. But he said, "I'm more optimistic now than I have been in my entire political life."

At least three Democrats -- Attorney General Stephen H. Sachs, Baltimore Mayor William Donald Schaefer and House of Delegates Speaker Benjamin Cardin -- are expected to seek their party's nomination for governor.

Committee members include U.S. Sen. Charles McC. Mathias Jr. (R-Maryland), and Reps. Marjorie S. Holt (R-Anne Arundel) and Helen Delich Bentley (R-Baltimore County). The committee also includes several Democrats.

While Nichols and members of the new committee said they had been greeted with plenty of enthusiasm, they said they wanted to make certain the enthusiasm can be translated into victory. "I'm not going to leap in until we determine that it's winnable," Nichols said.

"It takes more than enthusiasm from a small group," said Patrick McCuan, a Howard County developer who headed Nichols' county executive campaign and switched to the Republican Party just last week. Among other things, he said, the committee will figure how much money is needed and develop plans for organizing local support.

McCuan, who is cochairman of the exploration committee, said there already exists the embryo of local organization in each of the state's 23 counties and in Baltimore. He said estimates of the cost of a winning campaign have ranged between $1 million and $3 million.

Richard P. Taylor, a lawyer and Republican National Committee member who is a cochairman of the exploration committee, said fund raising for a Nichols campaign will begin immediately.

The committee also includes former Maryland Sen. J. Glenn Beall Jr.; NASA Administrator James M. Beggs; Louise Gore, who ran for governor in 1974; Del. Robert R. Neall (R-Anne Arundel), the House minority leader who is running for Congress, and state Republican Chairman Dr. Allan C. Levey.