Hart tries to tread a fine line between tough campaigner and party 'spoiler'

Gary Hart has not given up. He will keep calling delegates, keep making speeches, keep pushing his ideas and turning out press releases. The struggle with Walter Mondale goes on.

''Welcome to overtime,'' Senator Hart announces.

At the same time, the senator - who trails Walter Mondale by more than 700 delegates - will avoid actions that would split the Democratic Party. Mr. Hart doesn't want a lot of the blame if President Reagan trounces Mr. Mondale in November, as some predict.

Hart and his aides still see a flicker of hope for their campaign, despite the numbers that say Mondale has it all neatly wrapped up.

''I guess we're a little crazy,'' a Hart aide says with a chuckle. ''But there are still possibilities.''

What are they? Hart and his aides point to several possible paths in the next few weeks.

First, they point to the polls. Hart hopes that within the next two or three weeks, the polls will show that he would be a far stronger candidate against the President. Not just a little stronger than Mondale. Much, much stronger. That argument is central to his strategy.

Using those polls to bolster his case, Hart would try to woo away Mondale delegates. This year, under new rules, no delegate is legally bound to vote for any candidate. If Hart could persuade enough of them to switch, he could block Mondale's nomination.

At the same time, Hart hopes the Federal Election Commission will soon conclude that Mondale broke the rules in accepting help from delegate selection committees. Hart argues that there was collusion between the Mondale campaign and the privately funded committees, in violation of federal election law. With the FEC supporting his position, Hart could go before the convention to demand that ''tainted'' Mondale delegates not be seated.

Finally, Hart will try to shape the Democratic platform into something closer to his own positions. He appeared Monday before the party platform committee to urge them to seize several issues from the Republicans, including defense, fiscal responsibility, tax reform, trade policy, scientific research, and industrial policy.

Hart, in an apparent reference to Mondale, said there was little hope of defeating the GOP with old Democratic policies.

''If we simply cling to the policies of our own party's past, we will only repeat our own failures,'' he said. ''The greatness of (Franklin D.) Roosevelt and (John F.) Kennedy, was that they broke with the past and moved us into the future with new proposals.''

Those close to the senator describe the next couple of weeks as a waiting period. During this time, Hart will reassess his prospects and look for movement his way in the polls.

Some news reports have indicated that in the name of unity, Hart has given up on challenging what he calls ''tainted'' Mondale delegates. But the facts are a little more complicated than that.

After looking at federal laws and party rules, Hart has decided that there is little he can legally do to block Mondale delegates beyond the complaint he has already filed with the FEC. Mondale apparently hasn't broken any party rules that would allow Hart to challenge the delegates in the rules committee.

This narrows Hart's room for maneuver. He doesn't want to go before the rules committee, get beaten on a challenge to Mondale's delegates, and then have to go to the convention ''looking like a loser,'' says a source close to the senator.

This means that Hart's entire strategy against the ''tainted'' delegates relies on an early decision by the FEC. The worst thing that could happen, insiders say, is that the FEC would rule against Mondale after the convention - after Mondale had the nomination itself. That wouldn't help Hart, or the party.

Hart's overtime strategy has risks. By pushing his campaign all the way to the convention, he walks a narrow line between being a tough campaigner and a party ''spoiler.'' Hart, however, has decided it is worth it.

Anyway, a Hart associate says, being a spoiler isn't always so bad. After all , the last major spoiler at a national convention was Ronald Reagan in 1976. The label didn't seem to hurt him in 1980.