No matter what the outcome, the national elections this week will prompt a reevaluation of President Reagan's political leverage.
The narrow range of Mr. Reagan's last-hour campaigning for Republican candidates - confined to a few conservative GOP enclaves in less populous states like New Mexico and Utah - by itself illustated how his political coattails have been markedly shortened since 1980, when he led a GOP electoral sweep.
If Mr. Reagan's personal campaign potency on behalf of his party had been enough to make a difference for beleaguered Republicans, he would have been used more, GOP strategists concede.
Much has been made of Mr. Reagan's personal popularity as a political force, and particularly of his first year in Washington, when the Democrats caved in time and again to a remarkably unified Republican onslaught. But even before this election, Mr. Reagan has been compelled, in recent months, to build a coalition with moderate Democrats - the ''spenders'' the Republicans have inveighed against in this campaign - to pass legislation.
The most favorable prediction for this week's outcome, for the Republicans, is a standoff. If the Democrats pull further ahead in the House, and closer to even in the Senate, Mr. Reagan may face a stalemate in the new Congress unless he changes his approach - from one based on unique personal powers of suasion, to a more self-effacing one of coalition building.
The latest Gallup Poll gives the Democrats a 10-point lead over the GOP in total vote, 55 percent to 45 percent. This suggests the Democrats are ''certain to add substantially'' to their current House majority, according to that polling organization.
Opinion analysts and White House experts point out that Reagan's personal popularity is actually fairly modest compared with other recent presidents. And the 21-point margin of his personal popularity over his job-approval rating is on the lower edge of the scale.
''Although President Reagan's personal appeal rating (60 percent favorable) is considerably higher than his current job performance rating (42 percent approval), his personal popularity - despite a widely held belief - is not disproportionately greater than his predecessors,'' says pollster George Gallup.
At critical points in their presidencies, Jimmy Carter enjoyed a 26-point margin in personal appeal over job performance in April 1980 (66-40), Gerald Ford with 25 points (69-44) in October 1975, Richard Nixon with 20 points (56-36 ) in his late Watergate days in August 1973, and Lyndon Johnson with 36 points ( 76-40) in July 1968 as the Democrat bowed out before Vietnam pressures.
The overstating of Reagan's personal clout may have arisen because of the ''surprise'' outcome of 1980, suggests Stephen J. Wayne, George Washington University presidential scholar. And in the current election, the White House has sought chiefly to forestall another ''surprise'' loss, which could greatly undercut the Republican's political effectiveness the next two years, Mr. Wayne says.
''In 1980, the elements of surprise were the Republicans winning control of the Senate, and Reagan's unanticipated victory margin,'' he says. ''It prompted Republicans in close elections to attribute their wins to Reagan, and in turn this contributed to his capacity to gain unified support in the House in his first encounters.
''It contributed to his ability to convince the public that he'd received in 1980 a mandate for his economic policy - when in actuality the public voted less for him than against Carter.''
The most damaging potential surprise in this week's election would be GOP loss of control of the Senate. ''That would be interpreted as a signal of repudiation of his policies,'' Wayne says. ''Reagan's fighting to keep a working majority in the Senate, like the one he's had in the House.
Reagan's personal clout may have been overstated, and may be less relevant to his fellow Republicans' prospects in 1982 than has been widely perceived. But his standing with voters also seems less affected by the recent economic bad news than have been the prospects of Republican congressmen.
The latest New York Times-CBS survey shows Reagan's job approval rating a shade higher than earlier this fall. At the same time, it shows the Democrats maintaining their lead in congressional races, buoyed by the public's increasing concern about the economy.
In general, Washington may have a harder time distinguishing between presidential popularity, performance, and political potency than does the public.
The danger in this election, warns Thomas E. Patterson, director of Syracuse University's Maxwell School of Citizenship and Public Affairs, is that the results may again be overpersonalized.
''1980 wasn't really a mandate for Reaganomics at all,'' Mr. Patterson says. ''The press, which misread that, would likely read a large Republican loss this time as a rejection of Reagan and Reaganomics. It would misread a large Republican win as 'Reagan back in the saddle.' ''
The impression of political fortunes riding on personal popularity has persisted in recent years. ''Ike was always thought to be a nicer guy than an effective leader,'' Patterson says. ''But Ike had no coattails.'' And in the 1980 election, much was made the public's high regard for Carter's character - a regard that could not stay the sharp thumbs-down vote on his effectiveness that November.