The withdrawal of Sen. Edward M. Kennedy from the 1984 presidential contest disappointed some Republicans who would have relished a match-up of the Massachusetts Democrat and President Reagan.

But the view from the White House is that the Democrats have now lost their most formidable challenger to Reagan, should the president decide to seek reelec- tion.

Vice President Bush, who has repeatedly predicted that Reagan will run again, said yesterday that Kennedy's decision was a "good" one for the GOP.

Bush, once a presidential contender himself, said Kennedy would have been a "formidable" challenger to Reagan and that the senator's withdrawal means the most difficult potential opponent to the president is now "out of the way."

Bush, who suggested previously that Reagan should make his intentions known as soon as possible about the 1984 race, told reporters at a luncheon yesterday that he doesn't think the Kennedy withdrawal will influence the timing of Reagan's decision on seeking another term.

White House officials have said the president may wait until next October to make that decision.

As evidence that he thinks Reagan will run again, Bush cited the president's choice of Sen. Paul Laxalt (R-Nev.) to assume the new part-time post of "general chairman" of the Republican Party.

Laxalt said he wouldn't have taken the job if he didn't believe Reagan would seek a second term. Others have pointed out that Reagan's choice of Laxalt would serve the president just as well if he decides to retire but wants to signal otherwise to preserve his strength in Congress.

Bush rejected that argument yesterday, saying Laxalt would not have taken on the additional responsibility if he knew that Reagan would not run again.

Bush said he has no plans to run in 1984. However, many Republicans rate him as a likely GOP front-runner should the president retire after one term.

Talking with reporters in the vice president's residence, Bush was joined by his wife, Barbara. When a reporter suggested that Nancy Reagan would pressure the president not to run again, Mrs. Bush responded, "I've never heard her say that."

White House political director Edward Rollins said that Kennedy's withdrawal would not alter the chemistry of Reagan's decision about 1984. While many Republicans would have enjoyed a Kennedy-Reagan contest, he said, "Reagan's decision will be based on how the economic program is working."

The official line at the White House has been that Reagan would not walk away from an unfinished job, and thus would be likely to seek reelection if he felt his economic program needed more time.

The other side of that predic- tion is the assumption that Reagan would have more difficulty winning election if the economy remains stagnant.

Rollins said Kennedy was the only potential Democratic contender who could claim a base of support like the one Reagan developed after he lost the 1976 GOP nomination to President Ford.

"Kennedy has it and the others don't," he said. "They've got to go out and fight" for the support Kennedy could have commanded, he added.

Rollins described Kennedy, the most prominent liberal in American politics, as potentially the strongest ideological challenger to Reagan. "There's nobody that turns crowds on ideologically like Kennedy," he said.

But, he added, Kennedy will probably be crossing Reagan's path if the president runs in 1984, serving as an "elder statesman" for the Democratic Party and one of its leading fund-raisers.

"We have not seen the last of Kennedy," he said.