President Reagan's daughter Maureen is expected to be a candidate for cochairman of the Republican Party, and that has thrown a curve into what would normally be a contest of pure political inside baseball involving a tiny universe of White House and party leaders.

At a relaxed summer meeting of the Republican National Committee, it was the one subject repeatedly discussed in private -- but almost never in public.

The job will open up next January, when incumbent Betty G. Heitman retires. At least five women have begun the delicate exploratory process required of those seeking the post.

While largely ceremonial, the post is the highest-level job now available to a woman in the RNC, assuming that Frank J. Fahrenkopf Jr. retains the chairmanship.

Both party and White House officials said Maureen Reagan has signaled an interest in the post. The possibility that she might get into the race has provoked considerable resentment among both prospective candidates, who think they would be run over, and some other members and officials of the committee, who think the job should go to an RNC member.

"I was born at night, but not last night. If Maureen Reagan gets in, I get out," one of the potential candidates for the post said, adding: "But I really want the job."

Another state party chairman quietly seeking to line up support said plaintively, "If the president's daughter gets in the race, who is going to stay in against her? Not me."

Reagan, who like other prospective candidates has reportedly been advised by party leaders against beginning a drive for the post until after the 1986 elections, said she would not "even think about that until" after November.

Other possible candidates include Jeanie Austin, chairman of the Florida GOP; Ebbie Spivey, Mississippi chairman; Evie Teegen, Minnesota national committeewoman; Elsie Vartanian, New Hampshire chairman; and Jennifer B. Dunn, Washington state chairman.

William Greener, political director of the RNC, said, in carefully worded comments, that until the elections are over it is unproductive "to talk about the next chairman or cochairman." Fahrenkopf is expected to seek reelection in January.

In addition, he pointed out that when the party controls the White House "decisions about these sorts of matters at a minimum involve the inclusion and participation of the White House." The comment appeared to indicate that party leaders will defer to the president in making the choice.

While a commonplace subject in private conversations, there was a high degree of reluctance to discuss Maureen Reagan's possible candidacy on the record.

A number of people cited an incident in 1982 when Reagan angrily rebuked Ed Rollins, chief White House political adviser, for the comments he made about Maureen Reagan's bid to win the California GOP Senate nomination. She reportedly complained to her father after Rollins said: "Her campaign has not caught fire . . . . She has been strident on some issues, and while the president has been scrupulously neutral, there is an impression that Maureen is not the overwhelming choice of the Reagan boys.