George Bush said today he is "reassessing" his status in the Republican presidential race after the bittersweet experience of seeing his biggest victory of the year obliterated by television projections that Ronald Reagan had gained enough delegates to cinch the GOP nomination.

Coming off a landslide win over Regan in Tuesday's Michigan primary, Bush was jolted back into reality by watching the ABC and CBS television networks described Reagan as the victor in the nomination fight, on the basis of their delegate projections.

He ordered his campaign manager, James A. Baker III, to see what effect the network assessments had on his prospects for raising the half-million dollars he said he needs for a challenge in Reagan's home state of California in the final round of primaries on June 3.

Baker said it would be "goddamn tough" to raise the money, and Bush told The Washington Post that without adequate funds for the California campaign, his efforts to win Ohio and New Jersey -- the other two highly populous states that vote on June 3 -- "might be an irrelevancy."

Bush beat Reagan by 57 to 32 percent in Michigan in his biggest win of the year. But Reagan gained 29 delegates in Michigan and another 18 in winning over Bush in Oregon. The United Press International scorecard used by The Washington Post says that puts Reagan at 986 delegates, 12 short of the 998 needed for nomination. CBS projected Reagan at 1,006, and ABC at 1,031, proclaiming him the winner. Reagan's own count shows him with 910.

President Carter, meanwhile, moved closer to the 1,666 delegates needed for the Democratic nomination with a landslide win in Tuesday's Oregon primary. He captured 26 delegates to 13 for Sen. Edward M. Kennedy. UPI estimates that Carter has won or is leading for 1,550 delegates to Kennedy's 823.

Campaigning in Ohio yesterday, Kennedy said Carter, if nominated, may finish third in November behind reagan and independent John Anderson and cost Democrats both houses of Congress.

"The Democratic nominee may finish in third place this fall if his economic program is a pale carbon of the Reagan policy," he said.

For weeks, Bush has known that Reagan would be at or near the 998 mark by the end of May and over that figure by early June. His hope, he said, was that by adding such states as Michigan, Ohio, New Jersey and California to his previous wins in Pennsylvania, Massachusetts and Connecticut, he could appear the stronger candidate in vital November battlegrounds and thus peel away some of Reagan's support.

"I can add and I hope I can substrate," Bush told a press conference here. Wooing delegates away from Reagan "is the only way I can do it." He said it was "enormously frustrating" to have his Michigan victory dismissed by the network newscasters. In an early-morning conversation with Baker, he ordered the reassessment of "how realistic" it is to continue.

In an interview with The Post, Bush said, "Michigan showed there is tremendous fluidity out there. I am extremely confident that we can win Ohio and New Jersey the same way. California is much more of a gambler's thing, but still a shot."

But he said there is "a big blanket of inevitability" about Reagan's nomination, and "the question is can we get the funds for California."

Baker said that Bush has money in hand for New Jersey and Ohio, but only $100,000 of the $600,000 he would need for a California media campaign. The campaign manager flew back to Washington at midday to confer with Bush fund-raisers and key supporters about the prospects for raising more.

One longtime supporters said yesterday the future of Bush's candidacy would be decided "collectively" at a meeting that has been called for a number of his friends and advisers.

Bush sounded philosophical about accepting the judgment of these close associates on the viability of his two-year, $15 million try for the presidency.

"There is a feeling out there," he said, "that people don't want the choice they've been told they've got" for 1980 between Reagan and Carter. Yet, in light of Michigan's television treatment, he said, "obviously I have to take a look and say, 'wait a minute. Maybe I'm too close to this. Maybe I've lost my objectivity.'

"I hate not to finish what I've started," the former congressman, ambassador, party chairman and CIA director said, "But if people I love and respect tell me it's time . . . I could do that."

One of those people, Michigan Gov. William G. Milliken, whom Bush credits with a major role in Tuesday's victory, told The Post this afternoon, "My inclination would be to suggest that he go on through June 3. But I'd like to take a closer look at the numbers. I know it's a longshot, but there is so much uncertainly this year. . . ."

There apparently will be no pressure for a Bush withdrawal from former president Ford, one of the few GOP leaders who hasn't jumped aboard the Reagan bandwagon.

Ford, who still harbors ill will because Reagan didn't campaign for him in 1976, has met in recent weeks with campaign manager Baker, who played a similar role for Ford four years ago, and Reagan manager Casey in recent weeks.

But Tuesday's results did nothing to change Ford's feeling that "the race should be allowed to run its course," said Robert Barrett, Ford's top aide, in an interview. The results "may mean something to the media and the other candidates, but as to him altering his position, no."

In Los Angeles, the Reagan camp seemed largely indifferent to reports that Bush might withdraw from the campaign. Echoing what Reagan has said on several occasions, manager Casey said. "That's Bush's decision to make."

Casey said there were "some pluses and minuses" to whatever course Bush follows. If he stays in, it might sustain some of the dwindling interest in that final round of primaries June 3. If he gets out, said Casey, it would stem "the commitment of time and energy to the primary process."

Asked whether he though that it would be easy to heal the wounds of the primary campaign and unify for the fall election, Casey replied, "There aren't any wounds to heal, no wounds at all.

There has been widespread speculation for the past month that Bush's real purpose in remaining in the race was to build up a claim to the vice presidential nomination, and some Republicans suggested that a withdrawal now -- which would spare Reagan from further pre-convention campaigning -- might be a gesture of good will by Bush to the likely nominee.

But that surmise was denied by both Bush and Baker, and those familiar with the candidate's thinking said he considers chances of being tapped by Reagan minimal.

One insider said the main reasons for remaining in the race were to finish the course and to keep a commitment to Bush supporters in states like New Jersey, Ohio, Texas and Iowa, who are still fighting for delegate positions in upcoming primaries and state conventions.