His popularity sagging in the public opinion polls, President Carter traveled to this Democratic stronghold yesterday with the message that he worries litle about the polls or the political consequences of his actions.

At a nationally televised news conference here, the president was asked about a recent Harris Survey showing him losing in head-to-head contests with former president Ford and Sen.Edward M.Kennedy (D-Mass).

"I've never been particularly excited by very good polls and never been particularly concerned by very poor polls," Carter said. "They go up and down as you know."

But while the president was being "nonpolitical" at the news conference, it was mostly politics - including the need to shore up his own popularity - that brought him ot Illinois, a state he lost to Ford in the 1976 election.

Last night, Carter was scheduled to mingle with about 7,000 of the faithful from the Cook County Democratic Party at a $100-a-plate fund-raising dinner at the Conrad Hilton Hotel.

Before the dinner, he also planned to put in an appearance at a much smaller, $1,000-a-person reception for Alex Seith, the Democratic candidate for the Senate this year in Illinois.

Carter is scheduled for more of the same today, attending a fund-raising breakfast for Michael Bakalis, the state comptroller and Democratic candidate for governor, in Springfield after he speaks to a joint session of the IIIinoia legislature.

In the city where jobs and the delivering of other favors are the lifeblood of politics, the president assumed a decidedly nonpolitical stance at a news conference that included few questions on domestic issues.

But in answer to those questions, Carter's central theme was the same - a studied indifference to political problems plaguing his presidency.

He said, for example, that he is "willing to take the political heat" in cutting back federal spending to control inflation. And he sid the same in answer to a question about a local controversy involving the possible closing of three military bases here.

In response to another question, Carter stated that he will veto the Senate-oassed version of a bill that would impose tolls for the use of federal waterways.

The political flavor of this trip - and the fact that the White House is now taking presidential travel more seriously - was evident as Air Force One arrived at O'Hare international airport in hot, sunny weather yesterday afternoon.

The president led a large contigent of IIinois members of Congress, headed by Sen. Adlai E. Stevenson III, off the plane to be greeted by local officials and about 500 Democratic supporters, including children from nearby parochial schools, who were bused to the airport for the occasion.

Although the congressional delegation flew on Air Force One, they spent only about 15 minutes of the 75-minute flight with Carter, who spent most of his time reading briefing books preparing for the news conference.

Early in the administration, Carter imposed severe limitations on the number of aides he would taken on these trips as he would taken on these trips as he sought to portray his presidency as "nonimperial." But recently, the president and his aides have concluded they must make better use of the resources of the White House to shore up Carter's popularity, including the use of White House aides during presidential trips.

Thus, the White House contingent that traveled to Chicago was unusually large and included two lobbyists from the congressional relations staff who presumably spent their time here looking after the IIinois Congress members.