All the pieces seemed to be falling into place for the Maryland Republicans last fall when Democratic Gov. Marvin Mandel was convicted on political corruption charges and several of his party's brightest prospects began fighting over the right to succeed him.

For the GOP to capture the governor's office, thought Republican leaders, the party only had to unite behind one of several attractive gubernatorial hopefuls and then steer him through the divided Democratic ranks right into the State House.

But GOP enthusiasm has turned to guarded skepticism, with two of the party's best possibilities, Anne Arundel County Executive Robert A. Pascal and Montgomery County Executive James P. Gleason having decided against running.

Just nine months before the election, the party still does not have a standard bearer.

"I'd say we have a bad case of the flu," observed Sen. Howard A. Denis (R-Montgomery), noting the dwindling number of prime candidates. "It might develop into pneumonia if we don't take the right medicine, which is recruiting a candidate fast, raising money and getting the fighting spirit."

"No doubt it's a setback," said Sen. John J. Bishop Jr. (R-Baltimore County) of the Pascal and Gleason withdrawals. "The longer we wait to get a candidate, the harder it's going to be to take advantage of an excellent opportunity to elect a Republican governor."

With five months left to file for office, only John W. Hardwicke, a one-time member of Maryland's House of Delegates and the Harford County Council, is actively seeking the Republican nomination in the September primary election.

Former U.S. Sen. J. Glenn Beall, who lost his seat by a landslide in 1976, is touted as the front-runner, even though he has not decided to run. Other possibilities are Louise Gore, the GOP's nominee in the 1974 gubernatorial race, and former U.S. Rep. Lawrence Hogan.

The shortage of Republican candidates willing to run for governor has raised questions about the health of the GOP at a time when it is given its best chance of capturing the State House since Spiro T. Agnew's election in 1966.

Just a few months ago, Republican strategists were confidently predicting victory this November, feeling that the seven Democrats jockeying for governor would hopelessly fracture their party and offset its 3-to-1 margin in voter registration.

The GOP leadership had hoped to unite all wings of the party behind a single slate of candidates by now, avoid a messy primary battle and conserve scarce campaign funds. They did not expect to be looking for someone to head the ticket this late.

Several Republican officials blame Pascal's lengthy vacillation for the shortage of GOP contestants. Now that the popular Anne Arundel official will not be competing for scarce campaign funds and party support, the path is clear for new prospects, the officials say.

Other Republican analysts view the leadership vacuum as the product of deeper problems affecting the party, a side effect of the GOP's traditionally narrow base in Maryland and poor policies at the party's state and national levels.

U.S. Sen. Charles McC. Mathias, Jr. (R-Md.) said the national party's stamp of conservatism during the Nixon years and its involvement in the Watergate debacle severely depleted the ranks of locally elected Republicans who could merge as statewide candidates.

"The goal of any political party is to be in tune with its constituency," Mathias said. "We did go through a period when there wasn't enough attention paid to the black population, and the problems of the cities have bot been a major concern of Republicans."

Republican strength in Maryland has so dwindled in the past 20 years that politicians like Mathias have to pick up large numbers of traditionally Democratic voters in Baltimore and Prince George's County to win a statewide election.

Because of their dependence on Democratic crossovers, Republicans who win statewide office end up "catering" to Democrats instead of helping local GOP organizations strengthen themselves in local elections, according to Sen. Bishop.

Few Republicans hold local offices in Maryland outside the small pockets of GOP strength in Western Maryland, the Eastern Shore and central Baltimore County. Of 188 members of the General Assembly, only 23 have Republican Party affiliation.

If they win local races, many Republicans avoid running for statewide office, according to Bishop, because they have nothing to fall back on if they lose. That is because of the GOP's sparse patronage, he said.

Patronage-rich Democrats often reward losing candidates with state jobs. For example, Thomas J. Hatem, who gave up his position as insurance commissioner in 1974 to run for Congress, was given back the post after losing the election.

Hermann K. Intemann, a key GOP strategist, who is now serving as Maryland's transportation secretary, said few Republicans seek statewide races because of the severe uphill fight they face for campaign funds and votes.

"Sometimes they look at the numbers against them and aren't willing to make the sacrifice," Intemann said of GOP politicians. "Maybe we should be hungrier than we are."

The state GOP, traditionally a minority party, has charted its way through especially troubled waters in recent years, as it has faced bitter internal ideological fights and a series of national and state embarrassments.

Perhaps the low point came in the early 1970s when Vice President Agnew, Maryland's one-time Republican governor, was forced from office amid charges of political corruption. Simultaneously, state GOP leaders were found to have engineered a scheme to inflate for public relations purposes the proceeds of a testimonial gala for Agnew.

After the Watergate scandal, the party began a concerted effort to rebuild itself and broaden its base. Last year, a black physician from Annapolis, Aris Allen, was elected state party chairman and the party has actively recruited new members.

Even with the party's "new look," many GOP leaders believe the Republicans' best chances fer this years' election lie with disunity in Democratic ranks and embarrassment caused by the political corruption conviction of Mandel and three of the Democratic Party's chief fund raisers, Irvin Kovens, W. Dale Hess, and Harry W. Rodgers III.

"The base for the (election) is the fairly substantial number of disaffected voters in the state who are damn sick and tired of politics as usual and are looking for something different," said Sen. John J. Cade (R-Anne Arundel).