The race for the Republican nomination for the U.S. Senate in Maryland, once thought to be an easy hurdle for former White House aide Linda Chavez, has taken an unusual turn recently with reports that several new GOP candidates -- including a black, a formerly Democratic county executive, and an ex-U.S. senator -- may enter the race.

Just six months ago the Maryland GOP was begging for a Senate candidate to enter the Sept. 9 primary campaign in Maryland, a state where Democrats hold a greater than 2-to-1 edge in registered voters.

"Suddenly Cinderella has a lot of suitors," said state Sen. Howard A. Denis, a Republican from Montgomery County.

George Haley, a lawyer and the brother of "Roots" author Alex Haley, said he was giving "serious consideration" to running against Chavez and businessman Richard P. Sullivan, the only announced candidates in the Republican race to succeed retiring GOP Sen. Charles McC. Mathias Jr. Republican sources said they expect Haley to enter the race soon.

In addition, Howard County Executive J. Hugh Nichols, a Democrat turned Republican who surprised GOP officials this year when he backed out of running in the Maryland gubernatorial race, may enter the race in June, according to a recent column by veteran political observer and Baltimore News-American columnist Frank DeFilippo. Nichols did not return phone calls this week.

Former senator J. Glenn Beall Jr., whose father was also a U.S. senator and whose family has strong Maryland GOP ties, said Republican activists have urged him to run. Beall said he was trying to assess his support before declaring his candidacy. Beall served one term in the Senate, from 1970 to 1976, and was trounced by Democrat Harry R. Hughes in the 1978 gubernatorial race.

The Democratic party has a stable of widely known candidates in the Senate race, including Hughes, Baltimore Rep. Barbara A. Mikulski, Rep. Michael D. Barnes of Montgomery County and Baltimore County Executive Donald Hutchinson.

The potential mix of GOP candidates -- a black, Haley; a Hispanic, Chavez; and an Irish Catholic-Bostonian, Sullivan -- would make a highly atypical roster for the Maryland Republican Party. Only Beall represents the traditional GOP core. Like Nichols, Chavez and Sullivan are former Democrats.

The crowded field also would change the political equation for the best-known candidate, say GOP officials, who in January predicted that Chavez would have an easy primary victory. GOP officials view Chavez as the most viable candidate in a general election campaign because they believe that, as a Hispanic woman with ties to President Reagan, she can appeal to blue-collar and ethnic Democrats who helped Reagan carry the state in 1984.

But some party activists claim that new candidates are cropping up because neither Chavez, who switched parties a year ago, nor Sullivan has caught on among party regulars.

The idea of a crowded Senate primary field concerns some national Republicans. Dave Narsavage, a spokesman for the National Republican Senatorial Committee, said additional candidates could "muddy the waters . . . . We are not interested in pursuing or attracting other candidates." He said a crowded field "increases the likelihood for a lot of bloodletting."

GOP officials said that Chavez already faces a tough fight against Sullivan, who has contributed $100,000 of his own money to his campaign and is running close to Chavez in Republican polls.

In an effort to make her campaign more aggressive, Chavez is replacing her campaign manager. She said yesterday that she planned soon to start a direct-mail campaign to Republican households and will begin a media campaign in late May.

Haley, a lawyer who lives in Silver Spring, was a state senator from Kansas City, Kan., from 1964 to 1968. He moved to the Washington area when he was appointed chief counsel of the Urban Mass Transportation Administration in 1969.

Haley is a close friend of Senate Majority Leader Robert Dole (R-Kan.), according to a Dole spokesman who said that Haley paid a courtesy call to inform Dole of his political intentions in Maryland. Haley has been involved in national Republican politics for a decade.

Allan C. Levey, chairman of the Maryland Republican Party, said that Haley ran unsuccessfully for Congress in Kansas and has been involved in presidential campaigns in Maryland.

"He adds an intriguing mix to the campaign," said Levey, adding that he is impressed with Haley's "fire in the belly." Haley is undeterred, Levey said, even though numerous friends have warned him that it would be tough for a black to win a GOP primary in Maryland.

Levey added that Haley's candidacy could bring more blacks to the Republican Party. "He's a credible candidate who happens to be black," said Levey, noting that Haley's ancestor, African slave Kunta Kinte, who was celebrated in Alex Haley's "Roots," landed in Annapolis in 1767.

Republicans said that DeFilippo's column in the Baltimore News-American set off a flurry of rumors about Nichols, but both state and national Republican officials said that Nichols had not contacted them about running.

Sullivan, a former chief executive officer of Easco Corp. in Baltimore, has lived in Maryland for 22 years but has not been active in Republican politics.

Like Chavez, Sullivan is building a statewide organization from scratch. Some Republican activists in Maryland say that Sulllivan has been more aggressive in tapping local party regulars, while Chavez is spending as much time in her campaign appearances wooing Democratic voters as GOP voters who will choose the party's nominee in the primary election.

Edward J. Rollins, former White House political strategist and now Chavez's chief political adviser, said that Chavez is trying to do both because she has to begin to reach out to Democratic voters now to persuade them to vote for a Republican in the November general election.

"You certainly can't discount the primary . . . . You have to build an organization that will work in the general election," said Rollins. "In some cases, that means bypassing the traditional party activists."