President Carter's reelection campaign chairman, Robert S. Strauss, predicted yesterday that Carter will defeat Republican Ronald Reagan in November if he can make the former California governor "the big issue" in the fall.

Asserting that "there has never really been a big examination of Ronald Reagan," Strauss told a group of reporters:

"I think Reagan will be a big issue and get a massive examination -- what people believe he's accomplished. That's what we have to do -- keep him the big issue."

Despite the president's losses to Sen. Edward M. Kennedy (D-Mass.) Tuesday in the New York and Connecticut primaries, Strauss said he remained confident that Carter will win the Democratic nomination.

He said the Carter campaign at this point is ahead of its own projections on number of delegates won, with plenty of resources left to fight Kennedy as long as it takes.

"I know the senator is having his day in the sun," Strauss said. "He's worked hard, and is entitled to it. But we don't want to get sidetracked."

Strauss predicted that the president will win the Wisconsin and Kansas primaries next Tuesday and the April primary in Louisiana.

Strauss also predicted that if Kennedy wins enough primaries to become viable as a challenger, he will be subject to a renewed examination by the press that will show a "flexibility on the issues" that amounts to "political opportunism."

"When Kennedy becomes a factor again in the election, he gets his negatives as well as his positives," he said.

Strauss insisted that Carter has been damaged by his pledge not to campaign openly until the American hostages in Iran are released. He said there will be no change in this posture for at least 10 days, but predicted that soon the president may travel outside Washington for other than overtly campaign purposes.

For example, Strauss said, the president may make public appearances to promote his new anti-inflation program in states where there is not an immediate political test between him and Kennedy.

"My personal guess is that he will come out and do public things that will help his campaign efforts," he said. "They would be removed from politics, but he would hope to reap some political benefits from it."

Strauss said Carter could rally the public behind his economic program with a series of public appearances around the country, and said, "the time is just about right for him to start moving out."