With the impact of the Maryland primary diluted by its late position in the long election season, turnout is expected to be low today as voters go to the polls to choose their party's nominees in the presidential contest, one U.S. Senate race and eight congressional contests.

For one presidential candidate and a handful of surrogates, the final day of campaigning was low-key, a time of square dancing and listening to senior citizens sing and fighting futile last-minute court battles over who should tell the voters what at the polls.

Rosalynn Carter did the square dancing, after she had finished telling senior citizens in Baltimore County that her husband had worked to make sure there were no cuts in Social Security and other government programs for the elderly in the last four years.

Edward Kennedy, President Carter's Democratic primary opponent, did the listening, after telling senior citizens in Silver Spring that he, too, opposed Social Security cuts.

And Republican George Bush's campaign forces waged the short-lived court battle in an unsuccessful attempt to force state Elections Administrator Willard Morris to post signs at all 1,511 Maryland polling places telling voters that John Anderson was no longer a candidate in the Republican primary.

Republican frontrunner Ronald Reagan's forces kept the lowest profile, continuing to man their telephones -- the only weapon they have had to fight with in their money-starved campaign effort.

None of their efforts appeared likely to increase interest in the presidential primary, which has failed to attract widespread interest even among elected officials and party regulars.

Willard Morris, the head of the state election board, predicted yesterday that voter turnout would not exceed 40 percent. In Prince George's and Montgomery counties, officials variously predicted turnouts between 40 percent and 55 percent, about average for a presidential primary.

A low turnout is expected to hurt the two underdogs in the presidential race, Democrat Sen. Edward Kennedy and Republican George Bush, who have campaigned hard in the hopes of bolstering their fading candidacies with a win in Maryland.

A victory for Bush or Kennedy today would probably give their campaigns little more than momentum, however. Because of the state's delegate apportionment rules and the expected closeness of the final votes, the 59 Democratic delegates and 39 Republican delegates are likely to be divided fairly evenly between opposing camps.

Jimmy Carter and Ronald Reagan, who offered only limited campaigns in Maryland, will be watching the delegate counts closely. Carter is only 191 delegates short of the number needed for nomination, while Reagan is 167 delegates short. With the Nebraska primary, a total of 83 Democratic and 55 Republican delegates will be chosen today.

There is a wild card factor in both of Maryland's presidential races. Democratic voters may cast their ballots today for "uncommitted to any presidential candidate," while Republicans may still vote for Rep. John Anderson, who withdrew from the Republican nomination race to run as an independent. An attorney for the Bush campaign, Warren Rich, predicted yesterday that Anderson could take as much as 6 percent from Bush's total.

The Bush campaign's court challenge to the state elections board began at about 11 a.m. yesterday when the elections administrator was ordered to appear in Anne Arundel County Circuit Court. It ended three hours later with Circuit Court Judge Morris Turk rejecting the Bush campaign's request for polling place signs saying that Anderson was no longer a candidate for the Republican nomination.

"I don't think I have the authority to dictate what the Board of Elections should do," said Turk moments after the ruling. Maryland election laws, he said, "have no provision to cover this sort of situation."

Morris, the state elections chief, said that to inform voters at each polling place about Anderson's independent status would have cost thousands of dollars. Such signs were placed at D.C. polling places during last Tuesday's District primary.

Few last-minute histrionics marked any of the other state contests, as most of the state's representatives on Capitol Hill are expected to have little difficulty overcoming their primary opponents.

Charles McC. Mathias, the state's senior senator, is expected to defeat his five Republican primary challengers with ease, particularly since he has put a substantial amount of money -- at least $170,000 -- into this first step of his race for a third term. On the Democratic side, a dozen candidates are scrambling for the right to oppose the popular Mathias in the fall elections.

Montgomery and Baltimore counties have the two most closely contested congressional races in the state -- Montgomery's Republican primary and the dogfight in Baltimore County to unseat incumbent Democratic Rep. Clarence D. Long.

In Montgomery, former Republican Congressman Newton I. Steers is trying to hold off challengers Constance Morella, Robin Ficker and Phillip Buford so he can fight a rematch this fall against incumbent Rep. Michael D. Barnes, the man who beat him in 1978.

There will also be school board primaries in Montgomery and Prince George's counties, which will be open to independent voters as well as to registered Democrats and Republicans. Under state law, Independent voters are barred from voting in the party primaries, and there is no crossover voting allowed in Maryland.