President Reagan contended yesterday that passage of his tax bill marked "a new renaissance in America" which puts the nation on the road to "that new era of prosperity we all want."

The White House and its Republican and conservative Democratic allies gave Reagan full credit for winning this decisive victory, just as the country is now likely to hold the president fully accountable for whether his promises come true.

Reagan's rhetorical ace in the hole, in his skillful, nationally televised appeal to the nation Monday night, was his claim that his economic program could not work "piecemeal" with anything less than a three-year tax cut. Translated politically, this meant that on-the-fence members of Congress who voted against the Reagan plan could expect a presidentially led campaign against them in the 1982 elections, blaming the Democrats for everything that had gone wrong.

This is the sort of campaign that Reagan, with his superior communnicative skills, would be almost certain to win. Now, his victory has deprived him of this easy political course and has given the nation a chance to judge his program by its results.

As if recognizing that his victory could eventually put him on the spot, Reagan dodged a little yesterday on the question of when his economic programs would start showing results.

The president reminded reporters that the nation had been "a long time, decades, in coming to where we are, and we're not going to cure this overnight."

But the president was so proud of his victory that he didn't stop with this careful hedge. It is no secret in the White House that Reagan thinks his program will show results, and quickly, and his remarks yesterday evening indicated as much.

"As a matter of fact, I think the very fact of its passage before the program begins to show results is going to have a psychological effect that we will see in the expectations of the people," Reagan said.

The hope and expectation in the White House is that the financial markets at long last will react favorably to the Reagan economic policy, giving the economy the boost that administration advisers have been forecasting for several months.

"No one should doubt the difficulties we still face," the president said in his statement. "But we have made a new beginning. We're back on the right road, and we're making progress. And if we keep working together, we can reach that new era of economic prosperity we all want."

The president's optimism is not shared by the nation, according to the latest Harris Survey, conducted by telephone between July 8 and July 23.

Harris found that Americans, by a 56-to-33 per cent majority, do not think that a year from now the rate of inflation will drop below 10 per cent. Sixty per cent of Americans in the pool were convinced that a year from now "interest rates on borrowing will not have come down sharply."

This pessimism is viewed as a political plus by many of the president's closest aides, who think it will lead Americans to be satisfied with smaller results than the Reagan program promises.

Balanced against this is the likelihood, already acknowledged by White House chief of staff James A. Baker III, of some backlash against the Reagan administration this fall when cuts in social services begin to take effect. The pain caused by the budget cutbacks could well make lower-income Americans impatient for quick results from the Reagan program.

Another potential political liability is that the Reagan tax bill, as passed, is so loaded with benefits for the oil industry and the thrift institutions that it will create a larger deficit than anticipated. This could force Reagan to seek cuts in the now-sacrosant defense budget, which would provoke criticism from some of his most ardent supporters.

But these worries are in the future. Yesterday was a day of triumph for Reagan, a day in which the economic test he wanted was presented by a compliant House to the American people.

Summing up the program on which his administration is likely to be measured, the president said of the congressional action: "It has . . . removed one of the most important remaining challenges to our agenda for prosperity."