Ronald Reagan's remarkable turnabout on oil profits during his first 24 hours as an announced presidential candidate followed an intense backstage power struggle over just what the front-running Republican ought to say to the voters.

In his taped television speech to the nation Tuesday night, Reagan appeared to say "maybe" on the oil profits tax in Congress. That reflected high strategy by campaign manager John Sears. But Wednesday afternoon at a labor union hall in Boston's Dorchester section, Reagan was attacking "what is called the windfall profits tax." That reflected persistent urgings from his newly unveiled chief campaign spokesman: Rep. Jack Kemp of New York.

This back-and-forth was part of maneuvering, negotiating and bickering behind the scenes for weeks before Reagan's announcement. It helps explain why Reagan, for 15 years a master of the political campaign platform, seemed off his form in a shaky start.

The fact that the Nov. 13 announcement was so late fits Sears' overall strategic premises: with Reagan likelyto clinch the Republican nomination quickly, he should lie low as long as possible, and, when he does announce, aim at winning over non-Republicans. That means convincing them that Reagan is for the common man.

For more than four years, Sears has tried to cool the enduring love affair between Reagan and corporate business. He never quite succeeded in 1976, but this time was determined to make his point in the announcement statement, whose drafting began back in July.

Sears also had another project: to enlist Kemp, perhaps the Republican Party's most dynamic young figure. While Kemp's closest advisers were urging him to mobilize his business world following for his own presidential run, Sears courted him to jump aboard the Reagan bandwagon. Kemp finally agreed in principle when Reagan endorsed Kemp's supply-side economics, as exemplified by the Kemp-Roth tax reduction bill to restore incentive.

But agreement in principle was not the same as agreement in fact. The announcement statement was negotiated, paragraph by paragraph, over two months by Reagan and Kemp agents. What nearly prevented agreement was an ambivalent paragraph on oil profits. Kemp has assailed President Carter's tax as a menace equivalent to the depression-making Smoot-Hawley tariff. But Sears and other Reagan advisers worried that their man would become a front man for Exxon.

A bargain was struck in the final hours before the announcement. Reagan would keep this statement so obnoxious to the Kemp circle: "I don't believe we've been given all the information we need to make a judgement about this [oil profits]. We should have that information. Government exists to protect us from each other." To Kemp's colleagues, Reagan was joining the demagogic oil-baiting of Carter, Kennedy and Howard Baker.

To accept that statement, Kemp exacted a heavy price: the decisive policy role in Reagan's campaign. He will dominate Reagan's economic policy speech. What's more, Reagan almost immediately began retreating from Tuesday night's muted oil-baiting.

Arriving in working-class Dorchester the next afternoon (though precious few local residents were present), Reagan attacked the windfall profits tax as something that would eventually cost the consumer ("You're going to pay it"). Responding to our question, he said he would have voted against the tax approved by the Senate Finance Committee and supported by Senate Republicans.

Kemp's dominance in Reagan policy-making is widely interpreted as provoking the unexpected return to the Stanford University faculty of Dr. Martin Anderson, Reagan's research chief. Anderson does not go nearly so far as the Kemp circle toward supply-side economics and, though he will still support Reagan, would not be comfortable as a full-time staffer any longer.

The economic debate is not the only point of friction. The initiative for a"North American accord" between the United States, Canada and Mexico fits Sears' quest for a more moderate image. But one key adviser argued until the end against it, contending that the American public wants the old Reagan demanding of Iran: "The embassy hostages alive, or the ayatollah dead."

Under these conditions, Reagan's third and most carefully prepared presidential campaign began with him off balance. His taped television speech was uncharacteristically bland. His Dorchester speech was more vintage Reagan, but in its rousing moments dredged up outdated material from 1976 and earlier. Both John Sears and Jack Kemp might well heed warnings that Ronald Reagan is not easily reprogrammed.