It's a year in Maryland politics that shows the power of incumbency, and the best example is at the top of the ballot. Gov. William Donald Schaefer seems to be overseas as much as he is on the campaign trail.When Marylanders vote in the Sept. 11 primary election, they will face an extensive ballot but few competitive races, at least at the state and congressional levels. Things could heat up by the November general election, but the prospect now is for a low-key season. Voter registration is lagging, and, unlike the gun ban of two years ago or the gubernatorial race of 1986, no single campaign has ignited voters statewide.

Leading the Democratic field is Schaefer, who has banked away nearly $2 million in contributions and maintained a full schedule of state business that included a trip to Taiwan less than a month before the primary.

So seemingly confident is Schaefer that his reelection effort has been cloaked not in standard political rhetoric, but in a campaign of civic boosterism that presumes he will be around for four more years. The "Campaign for Maryland" is promoting civic activism on the environment, education and substance abuse, along with promoting the reelection of Schaefer and Lt. Gov. Melvin A. Steinberg.

Challenging him in the Democratic primary is Fred Griisser, leader of the group that unsuccessfully opposed the state's effort to prevent the sale of cheap handguns, a law backed by Schaefer.

Griisser, who has raised only a few thousand dollars, says his campaign seeks to give a choice to "normal" voters, ones he contends are tiring of Schaefer's spending and perceived arrogance.

On the Republican side, the GOP was set to challenge Schaefer with William S. Shepard, a retired foreign service officer from Potomac who was expected to offer an articulate attack on Schaefer's first term. But when he named his wife as his running mate for lieutenant governor, the deal came undone; perennial Republican challenger Ross Z. Pierpont, a retired surgeon from Baltimore, entered the race just minutes before the filing deadline, saying Maryland should not be a "one-family state."

Pierpont has put a kink in Shepard's fund-raising, and party regulars have not ruled him out as a possible victor in the primary. Shepard, meanwhile, has stayed a course of bull roasts and candidate forums, trying to spread his name outside of Montgomery County, where he ran unsuccessfully for Congress in 1986.

Among the statewide issues of note this year are taxes, growth and abortion.

Tax limitation measures are scheduled for the general election ballot in four counties -- Montgomery, Howard, Anne Arundel and Baltimore -- but a recent court decision may render them meaningless. Growth is also the main issue in Montgomery County Councilman Neal Potter's challenge of County Executive Sidney Kramer.

Abortion appears to be having a more selective impact, but heavy nonetheless in the districts where it is an issue. In Democratic primaries in Montgomery and Prince George's counties, abortion-rights candidates are mounting challenges against four antiabortion senators who participated in last spring's filibuster of legislation that would have guaranteed continued access to abortion.

Neither Maryland U.S. senator is up for election this year, and incumbents have the advantage in the contests for seven of eight U.S. House seats.

The one exception is in the 1st District, where U.S. Rep. Roy P. Dyson is facing a spirited primary challenge after controversy two years ago over the suicide of his chief aide and the disclosure of Dyson's close ties to defense contractors.

He is challenged by state Del. Barbara O. Kreamer (D-Harford), who has campaigned against Dyson's reliance on political action committee money and his opposition to abortion, and two other Democrats.

For the GOP, the 1st District presents the best chance to translate the registration gains of the past 10 years into a victory at the polls. Eight hopefuls will square off in the primary, a situation that has left Republicans enthusiastic about the level of interest but worried that an intraparty fight could weaken the eventual nominee.

Other officials up for reelection are Democratic Attorney General J. Joseph Curran Jr. and longtime Comptroller Louis L. Goldstein. Both face nominal opposition.

In Montgomery County, it seemed for months that Kramer, a former state senator and millionaire-businessman, would face only minor opposition in his quest for a second term as county executive. Then, at the last minute, Potter decided to enter the race, and the Democratic battle lines were drawn.

A 20-year County Council veteran who early this year announced he would not seek reelection, Potter, 75, has made the issue of development the cornerstone of his campaign. Drawing on his years as a civic activist, he has fashioned himself as a slow-growth, reform candidate and has repeatedly questioned Kramer's ties to developers. Recent campaign finance reports showed that Kramer had raised more than $243,000, much from business interests, while the Potter campaign has gathered $32,000.

Kramer, 65, has been outraged, he said, by "the innuendo" spread by "Mr. Potter and his agents," and has countered that his administration inherited most of the growth that has taken place in the county during the last four years. Further, he has bristled at attacks on his integrity, stressing that he has never been compromised by developers' generosity and has returned some contributions because he thought them inappropriate. His sound managerial record, he said, speaks for itself.

County residents also will vote for a County Council that increases from seven to nine members and will include council members from five districts as well as four at-large seats. All incumbents but Potter are seeking reelection, and all are included on a slate of candidates headed by Kramer called "the Democratic Leadership Team." Republicans see 1990 as a chance to break Democrats' 20-year hold on the council, and there are even Republican primaries, something rare in the county.

Abortion has become a dominant issue in the county's legislative campaigns, especially in District 17, where Del. Mary H. Boergers is running against antiabortion Sen. S. Frank Shore in the Democratic primary, and in District 18, where veteran Sen. Margaret C. Schweinhaut is facing a Democratic primary challenge from abortion rights leader Del. Patricia R. Sher.