The state Senate races in Prince George's are an example of the power of incumbency in a county long dominated by Democratic slate-making.

Democratic incumbents in five of the eight Prince George's Senate districts are widely considered shoo-ins in the Nov. 6 general election against inexperienced and poorly funded challengers. The two black incumbents from the Prince George's delegation, Decatur W. Trotter and Albert R. Wynn, face no opposition in the general election after eking out victories in hard-fought September primaries.

And Gloria Gary Lawlah, a delegate who defeated Sen. Frank J. Komenda in a fierce primary battle in September, also is running unopposed for the Senate.

In a county where registered Democrats outnumber Republicans by a 3-to-1 ratio, the five Republican challengers face uphill battles in their bids to unseat well-entrenched incumbents.

Incumbents interpret the dearth of strong challengers as a sign that county residents are pleased with their work in Annapolis. But the challengers, who insist that voters would benefit more from a competitive two-party structure, say the county's traditional practice of slate-making has discouraged candidates who are outside of the status quo.

"East Germany, Czechoslovakia, all throughout Eastern Europe, everyone has thrown out the one-party system and Prince George's still has it and it's strong as ever," said Republican R. Nicholas Palarino, who is challenging Sen. Leo E. Green in the 23rd District.

Preliminary figures show there are 195,096 Democrats registered in the county, compared with 60,445 Republicans. Another 27,820 voters registered without listing a party affiliation, according to the Prince George's County Board of Elections.

But Republican organizers, noting there are more Republican challengers in state and local races than in the past 10 years, say the fall election campaigns represent the party's effort to gain a greater foothold in county politics.

"We think the strongest boost for the Republican Party in Prince George's County is the increasing upward mobility of its population," said Richmond T.P. Davis, chairman of Prince George's County's Republican Central Committee. "These are people who might find their interest better served by the Republican Party. We are trying to build on that."

Two-party politics is more evident in state delegate races this year with Republican candidates, black and white, running in all eight districts in Prince George's. Voters in each district will choose three delegates and one senator.

The Prince George's delegation will face a prickly legislative session, as lawmakers grapple with issues such as abortion rights, an increase in the state's gas tax and income tax revisions, spawned by an independent review of the state's tax structure. Furthermore, voters in the county will look to state legislators to ensure that county schools do not lose state funding as lawmakers consider measures to increase state support for less affluent districts.

Of the five Republican challengers for the Senate, John Eugene Sellner is the only one who has previously run for elective office. An associate Realtor with Jim Hall Real Estate, Sellner is challenging state Senate President Thomas V. Mike Miller Jr. in the 27th District. Sellner ran for the 5th Congressional District seat in 1986 and 1988.

Miller, a longtime fixture in county politics and one of the most powerful politicians in Maryland, leads the county's top-to-bottom Democratic ticket along with County Executive Parris N. Glendening and 5th District Rep. Steny H. Hoyer.

Miller's campaign focuses primarily on the impact his influence in Annapolis has had in delivering goods and services to constituents in Prince George's, such as $5 million in state funds for the Prince George's Equestrian Center in Upper Marlboro and road expansions along Indian Head Highway and Branch Avenue.

The 27th District includes almost half of the land in Prince George's, stretching from Upper Marlboro southward to the Charles County line.

Miller, 47, a lawyer, has been in the Maryland legislature since 1971 and was elected Senate president in 1987.

Sellner, 60, said that if elected, he would encourage the Senate to rein in state spending to provide tax relief to Maryland residents. A Fort Washington resident, Sellner has criticized his opponent's role in making the practice of slate-making common in local and state politics.

Observers say Sen. Green, in the 23rd District, is the incumbent most susceptible to a Republican challenge because his district in the northeastern edge includes the county's largest concentration of Republican voters. Green's role in the eight-day Senate filibuster that killed abortion rights legislation in the General Assembly this year also has left him more vulnerable to challenge, as evidenced by his fierce battle to fend off abortion rights challengers in the September primary.

Green's challenger in the general election, however, is an anti-abortion rights candidate who agrees with Green's stand on abortion, if little else. A lifelong Republican, Palarino said he decided to challenge Green because he was unhappy with what he called the legislature's "perpetual increases in taxes." Palarino, 44, also criticized Green's record in providing services to constituents in the 23rd district, which includes Greenbelt, Seabrook and parts of Bowie and Mitchellville.

Green's campaign for reelection focuses on his record during 12 years in the legislature, which include providing state funding for road improvements and public transportation in a district where rapid development has begun to spawn traffic congestion. Green, a lawyer, is married and has eight children.

Palarino works for the Pacific Sierra Research Corp., a government consulting firm that analyzes U.S.-Soviet arms control positions. Palarino joined Pacific Sierra two years ago after retiring from the Army where he was the deputy special adviser to the president on arms control.

In the 21st District, Sen. Arthur Dorman is running against Republican candidate Abdullah Salim. Dorman is focusing on his record and influence in the legislature, stressing that his position as vice chairman of the Economic and Environmental Affairs Committee will help protect Prince George's state education funding at a time when state legislators are considering measures to bolster funding for more impoverished school districts. A 64-year-old optometrist, Dorman has served in the legislature for 26 years, the last 16 in the Senate.

Republican challenger Salim, 42, said new leadership is needed in the district, which includes portions of Langley Park, Beltsville and Adlephi. Salim cites his experience as a lawyer specializing in immigration and international law as a qualification to represent a district with an increasingly multi-ethnic constituency. The district is home to immigrants from Asia, Latin America, Africa and the Caribbean.

Running on what he calls a "human rights platform," Salim said he would work for programs to help disadvantaged children and curb the spiraling crime rate in the 21st District. Salim, a Sunni Moslem, noted that he is not affiliated with a member of the Nation of Islam, who ran in the primary election.

In the 22nd District, Sen. Thomas Patrick O'Reilly is challenged by Jack R. Jones, a Riverdale resident who is affiliated with the Libertarian Party.

Jones, a self-described househusband who works part time in organic farming, said taxes should be voluntary instead of mandatory. "I think that people are basically cooperative by nature and that people would be more willing to pay for services if the government was not all the time telling them that it was something they had to do." Jones, a former research scientist for the Bureau of Mines' Avondale Research Center, also said that property tax assessments should be amended so that property owners pay a one-time property tax at the time of sale, much like a capital gains tax.

O'Reilly, vice chairman of the Senate Finance Committee, said he provides voters with the experience necessary to make sure that Prince George's development projects will not be stalled by the current economic downturn.

"People are concerned about today's economy," O'Reilly said. "They want to know that there is someone in Annapolis who is going to make sure that the local economy doesn't collapse." O'Reilly, 52, a lawyer, has been in the Senate for 16 years.

Sen. Thomas M. Yeager is challenged by Guy L. Harriman in the 13th District, which includes a large portion of Howard County and the city of Laurel in Prince George's.

Yeager, a 54-year-old district sales manager for Hewlett Packard, joined the Senate in 1983.

Harriman, a lawyer with Harriman and Wylie, said he decided to run because he was frustrated by what he called the lack of a two-party system in Maryland.