Ronald Reagan seems back in the saddle again. The president stumbled at the economic summit and he is being battered by the Iran-contra hearings, but he is a happier man since he has returned to the stump to attack "the tax-and-spend crew on Capitol Hill."

White House chief of staff Howard H. Baker Jr. is said to lament that Reagan's return to normalcy has doomed a compromise with Congress that would significantly reduce the budget deficit and preserve the military buildup the president believes necessary to the nation's security.

But there was no sign of compromise when the president took his case against the Democratic-controlled Congress to Melbourne, Fla., last week. There was fire in his eyes and a lift in his step as he sailed through three speeches that bashed the "tax-and-spend" philosophy he said would return America to the "malaise and stagflation" of the the 1970s.

"I have always talked generally on one subject -- the growth of government," Reagan told me in an interview 19 years ago, midway through his first term as governor of California. It is still his favorite subject, even after 6 1/2 years as president in which he has never proposed a budget that would pay for the services he wants government to provide.

On the stump, Reagan lapses into reveries about the good old days in California where a balanced budget was constitutionally required and where he wielded the line-item veto power he now asks Congress to give the president. It seems so wonderful in retrospect that Reagan briefly drifted into the present tense while recalling his 943 line-item vetoes, as if he were still governor of California rather than a beleaguered president.

There were other lapses during the week. There always are, when Reagan is winging it. Addressing high school students departing for Europe, the president advised them to show respect for their ancestral countries, then told an Italian-American student that "they must have had a hard spring" in Venice this year because "all the streets seemed to be flooded."

Such performances inevitably encourage speculation that the 76-year-old president is slipping. The problem with this assessment, as series of aides have learned to their sorrow, is that disaster always has lurked close at hand whenever Reagan has drifted away from his script. When equipped with the boring addresses that seem to be the specialty of the current White House speechwriting team, it is understandable that Reagan attempts to enliven them.

If there is a sign of aging, it may be less in the lapses than in Reagan's increased resistance to even the mildest of excise taxes in order to get a budget deal. Reagan has always been stubborn, but he has accepted far higher tax increases in the past, claiming that he was "closing loopholes." This year's presidential budget rejected by Congress contained more than $20 billion in revenue hikes, unobjectionable to Reagan because they were called "user fees."

There has always been a conflict between Reagan's political rhetoric and Reagan's practice. In his first year in office as governor 20 years ago he signed what was then California's largest tax increase, contending that the budget gimmickry of his Democratic predecessors had made it necessary.

The secret of Reagan's effectiveness in his gubernatorial days and during his first term as president was that he was success-oriented. Aides who recognized that Reagan was an achiever devised ingenious rationalizations that allowed him to proclaim ideological purity while striking the political deals necessary for good governance.

Reagan is older and more stubborn now. He is a much tougher customer to sell a compromise, for Baker or anyone else. On the stump, Reagan conveys the impression of a secure ideologue who prefers to leave a legacy of intransigent opposition to fiscal compromise rather than of a president who gets things done. He appears delighted with confrontation when a genuine and useful compromise is at hand.

Reaganism of the Week: Speaking to high school "student ambassadors" Wednesday, the president said, "And yes, it's all right to have an affinity for what was the mother country for all of us, because if a man takes a wife unto himself, he doesn't stop loving his mother because of that. But at the same time, we're all Americans."