The Democrats who are lined up to declare their presidential candidacies cannot hope to match, in suprise and drama, the news that Senate Majority Leader Howard H. Baker Jr. (R-Tenn.) may quit the Senate and run for President Reagan's job in 1984 if Reagan doesn't.

The morning after this curious disclosure, the anteroom of Baker's press secretary was clotted with reporters, and the flurried receptionist said 30 telephone calls were backed up.

No one was sure whether Baker might be gearing up or is fed up--his frustrations with the Reagan White House are well known. Was he trying to force a decision on Reagan or telling him to step aside?

Something about it was not in Baker's decorous, professional style. It had the effect of an outburst.

Tom Griscom, Baker's press secretary, merely said of the story that it was "premature" and that Baker expects and hopes that the president will run again.

Baker's presidential aspirations may be taken more seriously in Washington than elsewhere in the country, despite his lame bid of 1980. His performance as majority leader, especially in the trying lame-duck session, brought him kudos on the "Nicholas Nickleby" order.

Republican senators, from Bob Packwood of Oregon on the left to Jake Garn of Utah on the right, give him superlative reviews for his patience, skill and endurance--and for rescuing them from the death grip of Jesse Helms of North Carolina and his ilk.

Baker has no more ardent fan than Warren Rudman of New Hampshire, a freshman Republican senator who goes about the Granite State describing Baker's presidential virtues. If Baker does go for it, he could count on the support of Rudman and his splendid organization in the nation's first primary.

His staff says that the story of Baker's intentions, long known, were to have been divulged Feb. 12. A leak was sprung, and the story broke on a day when another Baker--Baker, James A. III, the White House chief of staff--was expressing his frustrations. He told a reporter that Labor Secretary Raymond J. Donovan ought to go.

Somehow that added to the impression that Howard Baker was indulging in an uncharacteristic primal scream, " . . . and I'm not going to take it any more."

The Senate's Baker did a great deal of heavy lifting for the White House, at much cost to himself and to his small frame. Often he felt he was being cut off at the knees by White House hard-liners. His approach to government--conciliating, compromising, getting things done--is not theirs.

The lame-duck session apparently tore it for him. Although he had warned the president against having such a gathering, he came on with his usual good will. He went to parley with House Speaker Thomas P. (Tip) O'Neill Jr. on jobs. Reagan, who had tried to make O'Neill the heavy in the campaign, promptly announced he would veto a jobs bill.

When, after a succession of 22-hour days, Baker had rassled a continuing resolution on the federal budget through the Senate, word came out of the White House, from the hawkish National Security Council, that the president would veto it because of a ban on MX production. Baker was not amused.

But the low, and perhaps breaking point, came Dec. 8, when Baker was embarrassed before the Senate by Helms, the right-wing czar, whom Baker thought he was battling for the honor and glory of Ronald Reagan. Baker called up the renomination of Robert T. Grey Jr. as deputy director of the Arms Control and Disarmament Agency. Helms, as was his reflex, threatened to filibuster.

Baker had told the White House that he could get the votes for Grey, an unexceptional Foreign Service officer. It was no idle boast from a man who had singlehandedly saved the thoroughly discredited Clinch River Breeder Reactor for his home state.

Baker moved the nomination, whereupon Helms announced owlishly that he believed that the Grey nomination "would be withdrawn by the White House later today."

Obviously discountenanced by hearing inside information from the opposition, Baker dropped the debate on Grey.

For the president's leader in the Senate to be blindsided by the enemy was intolerable, even for a man of Baker's well-modulated ego. But it was more than that. Baker, who is is fairly conservative himself, apparently does not think the Republican Party should give way to extremists, especially on politically sensitive questions such as disarmament.

Subsequently, having bested Helms in the gas tax filibuster, Baker offered to push for Grey again. But the president, who, it turns out, was really after Grey's boss, Arms Control and Disarmament Agency Director Eugene Rostow, declined.

Premature or not, the Baker news sounded mighty like an expression of "no confidence" in the way things are going at the White House.