Hart or Mondale vs. Reagan?

Which matchup would give the Democrats a better chance to capture the White House? Would it be: Gary Hart vs. Ronald Reagan?

Or:

Walter Mondale vs. Ronald Reagan?

Senator Hart insists that this is the most burning question that will come before the Democratic convention in July. He argues that a Hart-Reagan contest would give Democrats a far better opportunity to send President Reagan back to retirement on the ranch.

The question is more than academic. New rules this year allow delegates to vote for any candidate they prefer, ignoring the voters in their home states. That's unlikely in most cases, of course. But Hart hopes to use this new delegate freedom to court a substantial number of Mondale delegates and throw the convention his way.

Does Hart's argument that he would be the stronger candidate this fall have merit? Would he really do better against the President?

The polls don't really tell us. The latest Gallup matchup, for example, indicates that as of May 5, Reagan could defeat Mondale by a margin of 50 to 46, a four-point difference. When Reagan and Hart are pitted against each other, the spread is 49 to 45 for Reagan, again four points.

Beyond the polls, however, it is clear that each of the two leading Democrats has special strengths.

Senator Hart does better with independents and moderate Republicans. Exit surveys taken during this year's primaries show that Hart would cut into Mr. Reagan's constituency in the white-collar suburbs, among well-to-do professionals, and among voters who dislike labor unions.

Mr. Mondale, on the other hand, is a favorite among traditional Democratic groups: labor unions, blacks, Hispanics, low-income workers, the unemployed, city dwellers, Jews, and Roman Catholics.

Hart argues that Mondale's strength among those groups should not be overrated. Those voters, many of them strongly anti-Republican, would vote Democratic anyway - whether the nominee were Mondale or Hart.

Mondale aides shoot back that Hart leaves many traditional Democrats cold. If they are not excited about Hart, they would refuse to work in the election and Democratic voter turnout would decline by four or five crucial points.

This debate is all-important to Senator Hart. He will go into the convention with far fewer delegates than Mondale. If he is to have any chance for the nomination, he must turn around at least 200 delegates now leaning toward Mondale - a feat that will depend on the ''electability'' issue.

Says Hart: ''Those delegates are committed, dedicated Democrats and practical people. They'd like to win this next election - for our country, for our party, and many of them for themselves. (They are) contending for governorships, Senate seats, House seats, and others. I think there is a very strong sense in this party that in many states and many districts, which are swing districts, that I would run more strongly than Mr. Mondale.''

Hart asserts that in the general election, Mondale would be carrying a heavy load of political baggage.

''In a contest with Mr. Reagan, I wouldn't have to answer for policies of the past, of the last administration. I wouldn't be on the defensive, responding to charges about high interest rates, or inflation, or something else. I can take the case to Mr. Reagan. I can put him on the defensive. . . . I represent a fresh start for this party.''

Those arguments are countered by political veteran Robert Strauss of Texas, who is supporting Mondale.

''The trick in this (election) is going to be to get the Democratic vote out, '' Mr. Strauss says. ''It is my personal opinion that Mondale gets the Democratic vote out better than Hart does, and with more enthusiasm because he is a more traditional Democrat. I think he is more appealing to older people, . . . minorities, (and) the blue-collar worker.''

There's another reason Strauss says he prefers Mondale. On the campaign trail this year, he asserts, Hart has done a poor job of projecting his message and his personality.

When the going got rough, as in the debates after New Hampshire, it was Mondale, rather than Hart, who looked more effective, he says.

Jim Johnson, Mondale's campaign chairman, says many doubts about his candidate's electability have been answered this year. As proof, he cites the South.

''One of the early ideas was that Mondale would find tremendous difficulty running in the South,'' Mr. Johnson notes. It was supposed to be John Glenn country. ''Some of those people who were most outspoken on the electability question have now seen Mondale winning Southern primary after Southern primary.''

There probably is no definitive answer to the electability question. If Mondale gets the nomination, and defeats Reagan, it will be irrelevant. If Mondale loses, Hart can always say, ''I told you so,'' and be in a better position for 1988.