The day-old "grass-roots" presidential campaign of former senator George McGovern has caused few apparent ripples in the camps of the other six Democratic contenders, but it reportedly has started to attract contributions and volunteers.

"I wouldn't say that 'pouring in' is the right way to put it," said Mark Kaminski, a McGovern aide at the Connecticut Avenue headquarters. "But we took in or got commitments for several thousand dollars yesterday. We're getting checks for $10, $100, $200 and a couple that were bigger."

McGovern opened his campaign with no campaign manager, no full-time fund-raisers, no party encouragement and no state organizations. Nonetheless, he was being treated as a serious candidate by party officials and other contenders.

The Maine Democratic State Committee is to meet Sunday to consider adding McGovern's name to the ballot for its Oct. 1 straw vote--a major test of voter sentiment.

A New York Democratic Party official said arrangements were being made to include McGovern among speakers at the Oct. 6 candidate forum in New York City, which is expected to produce the first real debate of the campaign.

Most of the rival organizations said their initial assessment is that McGovern will have little impact on the race.

"He changes nothing," said one pollster working on another campaign. "He has as much chance of a comeback as a guy who played pro football in 1972," the year of McGovern's last presidential race.

Reasons for discounting McGovern's impact included the scale of his loss to President Nixon in 1972, his 1980 defeat for reelection to the Senate from South Dakota and his unpreparedness.

"It's tough for anybody to start late," said a strategist for Sen. Alan Cranston (D-Calif.), "but it's tougher for somebody with McGovern's handicaps."

Several observers said McGovern may pose more of a problem to Cranston and Sen. Gary Hart (D-Colo.) than to anyone else in the race. His anti-war stands parallel Cranston's, and Hart got his start in national politics as McGovern's campaign manager.

But officials in both those campaigns seemed confident that McGovern's entry would not cost them either workers or contributors at this point.

"We have not seen any exodus of supporters," a Hart spokesman said.

At McGovern's headquarters, there was clear recognition of the work to be done to make his candidacy credible. A direct mail operation, using a list of about 200,000 likely contributors, is gearing up, Kaminski said. Names of volunteers are being screened for staff appointments. A nationwide television pitch is being prepared, with airing to begin "within 10 days or so, we hope."

McGovern's daughter, Mary, is serving as his deputy campaign manager. McGovern is writing most of his own speeches, including his announcement of candidacy delivered at George Washington University Tuesday.

The campaign headquarters is in the space used up to now by Americans for Common Sense, a lobbying group founded by McGovern to help combat the New Right. Kaminsky says ACS is being phased out of existence.

According to former McGovern aide George Cunningham, ACS netted some $2.1 million in two years. None of that is transferrable to the campaign, Kaminski said.

Henry Kimelman, chief fund-raiser for McGovern's 1972 race, is serving this time as a part-time adviser.

McGovern is to make appearances in the crucial early primary and caucus states of Iowa and New Hampshire and "may get into some straw polls," Kaminski said.