After the tax bill fight - a new political landscape

President Reagan has clearly changed his public image - from ideologue to vote broker - during this week's battle over the $98 billion tax hike.

Win or lose (the vote hadn't come at this writing), the President appears to have adopted a new strategy to deal with changed political realities. Basically, these are:

* Mr. Reagan's need to seek bipartisan support to govern effectively. The heady early days after the 1980 election, when Reagan's GOP juggernaut could plow through the Democratic opposition with total discipline, virtually all members aboard, are past. Reagan's victories will likely come harder now, assembled piecemeal on a pragmatic, not party-line, basis.

* National surveys showing the public's support for Reagan declining - down six points in NBC's national poll taken last week, down four in the Gallup poll and five in the Harris Survey, in their latest readings. The ABC/Washington Post survey, taken Aug. 17, has the President holding even with his June low. While Reagan's standing is not as low as President Carter's at this stage, and reflects the sophomore summer approval sags of other recent presidents, it helps explain the shift in tone from ebullience to a more dogged soberness in the administration's approach to Capitol Hill.

This was reflected in the White House's crusade for votes on the tax bill - a crusade waged so intensively, with such private arm-twisting and public pressure , it suggested a crisis, ''save the presidency'' spirit within the President's ranks.

* The split within GOP ranks, with many conservatives parting from Reagan on the tax issue. This reflects a renewed struggle for leadership within the Republican Party.

''Win, lose, or draw, Ronald Reagan remains the most precious asset of the Republican Party,'' says one Republican National Committee presidential loyalist.

''A struggle for the heart and soul of the Republican party is again under way,'' says a Democratic political strategist, active in fledgling presidential campaigns. ''If Reagan continues to buck the conservatives this term, and if he doesn't run again, the conservative hand would be strengthened in the '84 campaign. If economic results prove elusive, the conservatives like (Jack) Kemp ((R) of New York) will argue, 'I told you so.'

''If Ronald Reagan chooses not to run, the issue of the tax bill and economic policy of the summer of '82 will be the clarion call for the '84 presidential race within the Republican Party.''

* The President's reversal on taxes. This leaves the Democrats breathing a little easier for the November elections. The Democratic leadership sought to appear statesmanlike in backing the tax hike, reducing the risk of appearing obstructionist.

''The Democrats are well positioned for the fall campaign,'' says a Democratic strategist.

Basically, the tax measure itself had no wide public support. By 5 to 3, the public said they disapproved of the bill in the ABC/Washington Post survey earlier this week. Only three in 10 felt the bill would lower the deficit substantially. A majority thought the tax bill would not make taxes any fairer. And by 2 to 1 the public thought Reagan's economic program was not working.

''Reagan very much needs a perception that the economy is getting better,'' says Jeff Alderman, director of the ABC survey. ''To do that he needs to get interest rates down . . . he has to get business confident in his program . . . he had to get the tax bill passed.''

Political analysts saw Reagan's challenge this week as a test of his presidency - not only to adopt pragmatism on his economic program, but to convince reluctant members of his own party it's time to be pragmatic.

The decision by Democratic leaders - House Speaker Thomas P. O'Neill Jr. of Massachusetts and Sens. and Democratic presidential hopefuls Edward M. Kennedy of Massachusetts and Alan Cranston of California - to back Reagan puzzles presidential scholar James MacGregor Burns.

''I'm very surprised and intrigued that O'Neill and Kennedy and others have gone along with this bill,'' Mr. Burns says.

In classic political terms, going into an election, the opposition party usually poses alternatives. ''As a political scientist, I find this (lack of Democratic opposition) very disruptive in terms of the public's view of the election,'' Burns says.

''If Reagan's economic program proves not to work, Reagan in '84 can say the Democrats supported my tax bill and are responsible. If it does badly, they become implicated.

''Reagan seems to be moving from the role of the ideologue to the role of bargainer,'' Burns says. ''He is acting as broker.''