Just two months ago he was the Bush administration's favorite whipping boy, but these days House Majority Leader Richard A. Gephardt (D-Mo.) is getting the kind of velvety treatment normally reserved for the administration's best friends.

The courtesies include an invitation to the state dinner for Soviet President Mikhail Gorbachev, unprompted praise from President Bush for Gephardt's handling of the slow-moving budget summit talks (the majority leader chairs most sessions), similarly kind words from a senior White House official involved in the talks and a private breakfast last week at the State Department with Secretary of State James A. Baker III to review the summit before Baker flew off to Europe for a week of meetings.

Not that Gephardt has not reciprocated. The morning after Senate Majority Leader George J. Mitchell (D-Maine) sharply criticized the president for abandoning Lithuania in his rush to sign a trade agreement with Gorbachev, Gephardt spoke up at a White House meeting in support of the treaty and the president.

White House officials cannot explain the turn in the once-chilly relationship. "Maybe everybody just forgot they hate him," one Republican said. But the treatment has not gone unnoticed on Capitol Hill, creating puzzlement about the administration's motives. Is it accidental? Is it genuine? It is a setup?

Whatever it is, for now it's a 180-degree reversal from early March, when Gephardt delivered a speech attacking the president for "lack of leadership" and "lack of vision" in foreign policy.

Republicans tumbled over themselves in a coordinated counterattack. Within days, White House press secretary Marlin Fitzwater, Senate Minority Leader Robert J. Dole (R-Kan.), Senate Minority Whip Alan K. Simpson (R-Wyo.) and Edward J. Rollins, who heads the National Republican Congressional Committee, issued sarcastic statements dismissing Gephardt.

The president, who has made his distaste for Gephardt known in the past, also joined in. "I don't want to knock the man," he said, denying that Gephardt had gotten "under my skin." The president continued, "Maybe he'll come up with a good idea one of these days."

The administration took particular delight in denouncing Gephardt's March proposal for sending food aid to the Soviet Union. "Do you just want to put it on a ship and send it over there?" Bush remarked at the time. But the administration apparently has found many of Gephardt's other proposals appealing, having followed the majority leader's advice in several instances.

In his March speech, Gephardt said the administration's fiscal 1991 defense budget looked as if it had been written by someone who had not read the newspaper for a year and wondered why the administration wanted to spend more than $100 million on the Lance missile for West Germany "when it can only reach East Germany." In May, Bush decided to abandon the program.

Gephardt proposed the relaxation of restrictions on high-technology exports to Eastern Europe and the Soviet Union. Since then, in steps that have become increasingly liberal, the administration has proposed easing such barriers for Eastern Europe.

Gephardt also called for favorable tariff treatment for the Soviets, which is what Bush proposes in the newly signed trade treaty, if the Soviets liberalize their emigration law.

In May, Bush proposed a Citizens Democracy Corps for Eastern Europe. That sounded very much like Gephardt's call in March for a Free Enterprise Corps that would send Americans to East European countries to help them build their new democracies and economies.

Congressional Democrats suspect the recent White House stroking of Gephardt relates to the ongoing budget talks, but administration officials dismiss that thinking. "There's never been a time when anyone said anything about Dick unless in response to something he said about the president," one official said.

Administration officials appear as puzzled by Gephardt's support for Bush. "I was shocked he supported us on the trade agreement," one official said.

Neither side expects this truce to continue for long; there is too much history working against the Democrat who unsuccessfully sought the White House in 1988 and the Republican who won it. But for now the relationship between Bush and Gephardt has become temporarily -- and quite unexpectedly -- kinder and gentler.