Sen. John Glenn (D-Ohio) said yesterday that presidential straw polls are often unrepresentative and "subject to manipulation and abuse" and therefore he will not make any special effort to win them.

Glenn, generally considered one of the two top contenders for the 1984 Democratic nomination, said he instead will concentrate on winning delegates to the Democratic National Convention. Straw polls are essentially popularity contests and do not involve selection of delegates.

Glenn said that while it is not technically possible to withdraw his name from future straw polls, he will devote no extra campaigning or resources to them.

Glenn, who issued the statement through a press aide as he campaigned in Florida, has not made a great effort to compete in straw polls and has not done particularly well in them. But he is the first major Democratic presidential hopeful to state formally and on a blanket basis that he is not going to focus on the polls.

Glenn said he will address some or all of the gatherings at which future polls are to be held, and hopes his supporters will vote for him there.

But he said he will not hire added staff, allocate extra time, buy blocks of tickets for supporters, hire buses for them, rent hotel rooms for them or pay travel expenses to get people to the sites of staw polls.

Glenn's decision could reduce the unfavorable impact of any future poor showing and increase the favorable impact of any good showing.

Three major Democratic straw polls are scheduled for October: Maine on Oct. 1 to 2; Iowa, Oct. 8, and Florida, Oct. 22 to 23.

The polls have been criticized by some party professionals as giving the public a misleading impression of relative candidate strength because they often involve only a handful of party activists at functions like a party picnic.

The polls so far this year have produced some surprising victories for dark-horse contenders and defeats for the leading ones. In June, Sen. Alan Cranston (D-Calif.) defeated former vice president Walter F. Mondale in a straw poll in Wisconsin, despite the fact that Mondale was the heavy favorite because he comes from neighboring Minnesota. A week later a public opinion poll conducted by a Wisconsin newspaper contradicted the result, putting Mondale far ahead of Cranston in popularity.

Another popularity poll, involving Alabama Young Democrats, also gave Cranston a victory.