The timing was accidental. But when Sen. Edward Kennedy played host to President Reagan on Monday at a glittering fund-raiser for the John F. Kennedy Library, more than one message was being sent.

Top state leaders of the Democratic Party, in town for the meeting of the Democratic National Committee, were reminded by the photos and stories about the event that Kennedy wants very much to be part of the 1988 choice of Reagan's successor.

It is not the first such hint Kennedy has dropped. Last March, barely two months into Reagan's second term, he told the home-town Boston Globe that, "I'd like to be president someday," and no longer felt inhibited by the family concerns that he said kept him on the sidelines in 1984.

Back in March, he began what was seen as an effort to reposition himself and the Democratic Party, with a heavily publicized speech at Hofstra University. He warned that Democrats would continue to lose national elections if they remained "content with fighting a rear-guard action to save the policies of the past."

The man who challenged President Jimmy Carter from the left in an unsuccessful 1980 bid for the Democratic presidential nomination was reported, as The Washington Post said, to be "moving his party and his political image toward the center."

There is nothing subtle about the effort. Last winter, he was photographed in a smiling handshake with the Rev. Jerry Falwell, the Moral Majority leader, when they made a joint appearance at the National Religious Broadcasters convention.

Last week, when I went to his office for an interview, I was walked past walls of mementos of the Kennedy family to be shown a framed enlargement of a letter of praise he received last year for his concern about the men and women of the armed services and their families. The letter is signed by Sen. Barry Goldwater (R-Ariz.).

But for all the image-making, there simply is no evidence of a radical change in Ted Kennedy. His heart and his head are where they always have been -- at the left of the mainstream American political spectrum.

When the nonpartisan National Journal published its ratings of members of Congress early this month, Kennedy was ranked the most liberal of all senators on combined economic, social and foreign policy roll-calls in the last Congress.

He is off to a good start in his title defense. In his Hofstra speech in March, Kennedy said Democrats must show "the courage to discard" outdated programs. When the Senate was debating the budget in May, he voted to discard only two: a special school- aid program for districts with big government facilities, which every president since Eisenhower has tried to eliminate, and the general-revenue- sharing program enacted during Richard Nixon's presidency.

But on 24 other floor amendments, Kennedy voted to maintain or increase spending: for foreign aid, Medicare and Medicaid, legal services, Amtrak, the Veterans Administration, school lunches, Appalachia aid, rural housing, Head Start, student loans, postal subsidies, mass transit, urban development grants and a variety of other traditional Democratic programs.

At Hofstra in March, Kennedy said, "We cannot and should not depend on higher tax revenues to roll in and redeem every costly program." But the rejected Democratic budget resolution he helped shape and supported would have raised taxes $51 billion (mainly on corporations, he points out) to maintain higher levels of domestic spending.

At Hofstra, he warned Democrats against the "special interest" label that was so damaging to Walter Mondale in 1984, saying "There is a difference between being a party that cares about labornd being a labor party."

But when the defense bill was up in the Senate early this month, it was Kennedy who offered the amendment to restore the Davis-Bacon Act requirements on prevailing wage rates for military construction projects. That's a perennial issue of special interest to the AFL-CIO building trades unions.

The point is not that Kennedy is hypocritical but that, for all the rhetoric of change, his heart is where it always has been. Listen to him for an hour, and it is evident that the concerns that stir him are racism in South Africa and what he sees as the retreat on civil rights at home, famine abroad and hunger in America, unilateral U.S. military intervention in Central America, the need for nuclear arms control and, always, assuring adequate health care for all.

After hearing Kennedy, my strong sense is that he is not moving or shifting ground at all -- that if he is ever to be president, the country will have to come to him.

That seems unlikely if not impossible today. But Kennedy is only 53 years old, the same age Reagan was in 1964, when Reagan made his famous television plea for the lost cause of Goldwater's election. By 1980, the country's politics had shifted enough to put Reagan in the mainstream, and he reaped rewards for his own consistency.

It may be that Kennedy's guest of honor on Monday was really his role model. I find that possibility more plausible -- and attractive -- than the image-changing alternative.