Robert R. Neall, the Republican floor leader in the Maryland House of Delegates, announced today that he will run for the U.S. Congress seat being vacated by Republican Marjorie S. Holt.

Holt, a popular legislator who has represented Maryland's 4th District since 1972, is retiring at the end of next year. Today she appeared with Neall at the State House here and said she will work to get him elected.

She said the knowledge "that a superlative candidate was ready to succeed me" was a major factor in her decision to retire.

Local politicians are anticipating a lively race if Washington Bullets forward Tom McMillen also formally announces next month that he will run for the seat.

"There's some uncertainty about running against a personality or a celebrity," said Neall, 37. "That's why I decided to get into this thing early, and get my message out."

With Democrat McMillen apparently poised to run, Neall is already emphasizing his roots as an Anne Arundel County native -- McMillen has lived in the county since 1978 -- and his 11 years in the House of Delegates.

Holt's support is seen as an important factor for Neall in his bid for the nomination in the GOP primary.

She has received more than 60 percent of the vote each time she has run in the district, which also includes parts of Prince George's and Howard counties.

The endorsement "helps him because she is so incredibly popular over there," said one field worker with the National Republican Congressional Committee. "It gives him a lot of credibility."

A commercial banker from Davidsonville (who counts McMillen among his constituents), Neall was working part time as a legislative assistant in Annapolis and part time at his family's Davidsonville grocery store when he won his House of Delegates seat at age 26.

He describes himself as slightly less conservative than Holt -- although not a "raving liberal" -- and promises to place the same emphasis she has on constituent affairs.

With Andrews Air Force Base, Fort George G. Meade and the U.S. Naval Academy in his district, Neall said, he would be remiss if he did not try to replace Holt on the House Armed Services committee.

"Marjorie Holt's being so close to Mr. Neall at his announcement was a bit of a surprise," said McMillen's campaign manager, Jim Thompson. "I hope he's going to be his own man. While Mrs. Holt has declared that she won't be seeking office . . . it appears that she's running by proxy through Mr. Neall."

Thompson said McMillen, 33, wouldn't be running on basketball fame alone, but added that the competitiveness, teamwork, and pressure of professional sports are useful skills for politics.

He noted that McMillen runs his own car-phone and beeper company, has been involved in community organizations and was a Rhodes scholar at Oxford University.

While neither McMillen nor Neall are discussing campaign issues in detail at this stage, Neall said the budget deficit is a major concern.

Neall, a member of the House of Delegates' Appropriations Committee, said the state constitutional requirement for a balanced budget has worked well, and said he would support a similar effort in Congress.

So far, there are no other announced candidates for the Republican and Democratic nominations.