MORE THAN 1400 delegates gathering today at the Boston Sheraton for the state Republican convention will endorse a candidate for governor. And though it's difficult to predict the outcome of this afternoon's balloting, the most appropriate choice won't receive a single vote. Gov. Edward J King is currently seeking renomination as a Democrat.

At a time when national Republican leaders are distinguishing themselves by dissenting from rather than towing the party line, King has been almost aggressive in his support of President Reagan and fiscal policies. Top Reagan aides and G.O.P. leaders, uncomfortable with huge projected budget deficits have for some time been pressuring the president to tone down his initial proposals. Just last week, Senate Majority Lender Howard Baker (R-Tenn.) officially broke ranks, proposing a surcharge on income taxes; the next day Senate Budget Committee Chairman Peter J. Domenici (R-N.M.) called for defense spending cuts. At the same time, an overwhelming majority of state executives, headed by Republican Richard Snelling of Vermont pointedly stressed that their "concept of federalism differs in most significant details" from Reagan's.

But through it all, King has endorsed the Administration without any qualification King testified in favor of Reagan's budget in early 1981--ironically, while the governor's own aides were in Washington lobbying against some federal cuts: This January, King loudly praised the New Federalism. And at last week's governor's gathering. When his fellow Democrats unanimously declared that they are "appalled at the Administration's callous disregard of the elderly, farmers, college students, small business and unemployed workers, "King was conspicuously absent. Instead, he met personally with Reagan, declaring afterwards, "I see no reason why we should not have a tremendous vote" for the economic package.

JUST WHY KING makes those overtures to the President remains unclear. His aides claim that King-Reagan is a natural relationship stemming from the men's shared philosophical bent. Indeed, as governor. King has cultivated a tax-cutting, bureaucracy-streamlining Pro-business image. Critics call him obsequious. Two years ago, King embraced then-President Jimmy Carter as warmly as be now does Reagan. Other detractors say he is unstable "I don't know whether he's the real world or not," says King's predecessor and principle challenger, Michael S. Dukakis.

No matter how you account for King's fondness for President Reagan and his policies, their close ties could prove politically devastating. Other executives have been issuing dire warnings, adjusting revenue projections, and lobbying in Washington for relief King has, in effect, chosen to ignore the significant changes that Reagan has slated for federal state relations--most notably the proposed dumping of massive aid programs onto the states. King has asserted that "there were will be not winners and losers" under the New Federalism. Accordingly, he has drawn up a 1982 state budget that assumes an increase of $38 million in federal aid--at the same time that total federal aid to state and local governments is being slashed by 15 percent.

Much of King's brash confidence that Massachusetts can thrive under the new programs of Reaganomics seems only political positioning, election-year fact juggling. "Our economy is so much stronger than most other states," he boasts often and in testimony before the Joint Economic Committee he recently trumpeted "the great American success story" that has materialized during his reign. But though unemployment has inched down in Massachusetts in the past few years, the Bay State is hardly in the invincible position that King would suggest. Manufacturing for one key example, has stagnated over the past year, and several key cities have actually lost jobs since King took office.

KING'S INSISTENCE on the following the most optimistic projections, for both Reagan's programs and his own, has already made Massachusetts suffer. He has said "we can swallow" the chronic deficits in the Massachusetts Bay Transportation Authority budget. Yet subway fares have tripled in the past four years. He notes proudly a fall in welfare caseloads. But the success of this crusade has resulted not from a healthier economy, but from sticter requirements for qualification.

He talks improvements in the state education system, yet education may become more inaccessible to many students next year, when tuition at state colleges goes up by 10 percent. Under King's "revitalization of the economy," towns and cities have been forced to lay off policemen and firemen, and cut health services and basic assistance programs like snow plowing.

Ronald Reagan's New Federalism could "almost make you cry because it is so logical," King recently declared, praising that White House initiative. But his own illogical tendency to gloss over its imperfections has already hurt the citizens of Massachusetts, and threatens even more damage in the future. It could make you cry.