Maryland Republicans, who only a few weeks ago were depressed and demoralized over their embarrassing failure to field a credible candidate for the Senate, have been ecstatic in recent days over indications that White House aide Linda Chavez plans to enter the race.

Republican Party officials, particularly the younger party members, have convinced themselves that the presence of Chavez means 1986 will be more than just a shake-out period for the badly outnumbered GOP in Maryland; it will be a period of evolution.

"The old Republican Party, the country club Republican Party, is gone," said Brian J. Berry, chairman of the Maryland Federation of Young Republicans. Berry declared that the "new ideas" theme is not being sung just by Sen. Gary Hart (D-Colo.), but also by many young Republicans.

And Chavez speaks their language, added Bob Clark, president of the Montgomery County Young Republicans, which passed a resolution endorsing the 38-year-old White House director of public liaison.

In the past, the GOP in Maryland has been split into two camps, declared one young Republican. There were the progressive Republicans, such as Sen. Charles McC. Mathias Jr., who won reelection by developing liberal reputations on civil rights, economic and defense issues. And there were the conservatives, such as Rep. Marjorie Holt, who were supporters of higher defense spending and opponents of busing.

The progressives won statewide; the conservatives did not. But Berry and others said that conservatives can win in Maryland if they understand one key point: Many moderate, white Democratic voters may hold conservative views on defense and the economy, but may find it difficult to support a party that has a reputation of excluding minorities.

Chavez echoed that theme.

"The party continues to suffer under one specific criticism," said Chavez, in her first major public speech in Maryland since considering the Senate race. "There is a stereotype, and the stereotype persists, that the Democrats care about the 'have nots,' while the Republicans care only about the 'haves.' "

She said that if the GOP is going to attack welfare, and she thinks that it should, then it must come up with a better alternative.

"The rising of a healthy economy will not lift our boat, and I think we have to come to terms with that as a party," she said. She added that the GOP must promote programs "that have middle-class values and provide real jobs in the private sector."

Chavez, a former Democrat who switched parties in April 1985, served as staff director for the U.S. Commission on Civil Rights before joining the White House staff.

On the commission, she was a lightning rod of discontent for civil rights groups angry with her strong opposition to quotas. During her tenure, Chavez, who is Hispanic, referred to quotas and similar programs as white, liberal approaches that were condescending and misdirected.

In her speech, she criticized welfare for creating "dependency," and said that most federal job training programs fail because they do not recognize that poor workers sometimes need to learn other basic life skills, such as how to use an alarm clock, make a good appearance on the job or get to work on time.

Chavez appeared to please most Maryland Republicans, happy that a candidate with apparently strong White House backing is entering the race. But a few worried privately that she might not be well-grounded in local issues.

Even her boosters had one criticism: her lack of a formal announcement.

"She's going to have to come out soon, very soon. We're having candidates coming out of the woodwork," Berry said. "The fence-sitters have got to be kicked off the fence. We have to have a decisive candidate."

Some of the Republicans seemed intrigued by the announcement that Richard P. Sullivan, former chief executive officer of Easco Corp., a Baltimore toolmaking firm, would be entering the GOP Senate race. They said that Sullivan might be able to raise substantial money from the Baltimore business community, but they also appeared miffed that he has not consulted with party officials and has not been active in Republican activities.

The GOP enthusiasm, however, has not carried over into the governor's race, where Republicans said they would be happy just to have some fence sitters for now, after the withdrawals of Howard County Executive J. Hugh Nichols and former state senator Aris T. Allen.

"Hi, my name is Bob. Are you interested in running for governor?" joked one man as he moved through the crowd. Quipped another: "Let's see now. Does anyone know any other Orioles or movie stars in Maryland who are Republican?"