Democrats wonder how to build on uneven base of historic convention

It was a convention touched with a sense of history that picked Walter F. Mondale and Geraldine A. Ferraro as its standard-bearers here this week. It was also what political veteran Frank Mankiewicz called ''probably the most liberal convention'' in Democratic Party history.

As delegates packed their bags to leave this beautiful city by the bay, they were most excited, and most impressed, by the first-ever choice of a woman as the nominee for vice-president.

Yet even that moment in history was not enough to erase the concerns these delegates feel about this week, and about the campaign ahead.

There is no doubt that Mr. Mondale's choice of Representative Ferraro to share his ticket went a long way toward rescuing this convention for the man from Minnesota. But conversations with dozens of delegates - in hotels, in restaurants, and on the convention floor - indicated clearly that for many of the party loyalists here, the week was marred by the mistakes of the Mondale team.

A longtime Democratic insider, speaking privately with a reporter, estimated that the good and bad of this week were about equally divided. He said:

''Mondale got the main things he wanted here. He got the support of Gary Hart and Jesse Jackson. He got a platform he can be comfortable with. And there were no major fights on television to disrupt the message coming out of San Francisco.''

Further, he noted, Senator Hart's plea to the convention after Mondale's victory - ''there is a time to fight, and a time to unite'' - encouraged the healing process within the party. The Rev. Mr. Jackson's words also helped: There is, Jackson said, ''a time to compete, a time to challenge, a time to cooperate.'' But the party insider also observed:

''The appointment of Bert Lance as the Mondale campaign chairman, and the attempt to fire Charles Manatt as party chair, was a dreadful, dreadful blunder. It was incomprehensible when Mondale did it, and it remains incomprehensible.''

From a distance, many voters may look with surprise at the brouhaha over Mr. Lance and Mr. Manatt. It is, as one delegate observed, just insider politics. A member of Congress from Texas who supports Mondale noted that very few people in the United States decide whom they will vote for on the basis of who the campaign chairman is.

Even so, delegates here said over and over again that the Lance-Manatt affair could have an impact on the entire fall campaign. Why? Delegates offered several reasons:

* The attempt to fire Manatt, a California lawyer and banker, and replace him with Lance, a Georgia banker and close friend of Jimmy Carter, took the attention of the press off Ms. Ferraro. The choice of the Queens, N.Y., congresswoman for the V-P post gave a boost to Mondale, but the good news was submerged only two days later.

* The flip-flop on Manatt - he was fired, then rehired within a matter of 48 hours - made Mondale look indecisive. One story making the rounds here illustrates the point. Mondale supporters like to compare his position today to that of Harry S. Truman in 1948, when Truman overcame a huge Republican lead and won. The Manatt affair, however, had delegates comparing Truman and Mondale in another way. Truman fired Gen. Douglas MacArthur, a national hero, during the Korean war, and made it stick. Mondale, the delegates observed, could not even fire his own party chairman without backing down.

* Lance, an amiable man much liked by the press, was nevertheless forced to resign his job as Jimmy Carter's White House budget director when he was charged with wrongdoing in his banking business. Later he was cleared of all charges. But bringing him back in such a key post in the Mondale inner circle, in the opinion of many delegates, negates the Democratic argument that Mondale represents a higher set of ethical values than the Reagan administration. A number of delegates say the issue of ethics is now essentially lost. Sen. Ernest F. Hollings of South Carolina is so concerned that he told reporters at a breakfast meeting Thursday that Mondale should drop Lance entirely from his team.

* The treatment of Manatt was taken as a sign by many Westerners, especially California delegates, that Mondale was writing off the region in November. Otherwise, they asked, why would Mondale dump the hardworking, popular Manatt and make no compensating gesture toward the nation's most populous state?

Mondale - 13 to 15 points behind Reagan in the latest polls - needed all the help he could get from this convention. A good convention - and this was a smooth-running one - can boost a candidate by 10 to 15 points in the polls. But the Lance-Manatt affair shook the confidence of many delegates, who are now supposed to return to their home states and go to work for the ticket, and it blotted the week's press coverage.

Said a southern Florida delegate: ''The whole Lance-Manatt business worries me. I only have a certain amount of time to give to the party this fall, and I've decided to spend it all working on local races, rather than the Mondale campaign.''

Although the Lance-Manatt news dominated many hallway conversations among delegates, it should not be overlooked that there was also a great deal of very positive news for Mondale here.

Most important was the enthusiasm of the delegates for Ms. Ferraro. That enthusiasm carried Mondale through several problems he had during the week, including challenges from some blacks, Hispanics, and feminists.

The convention had the seeds of trouble. A very large portion of delegates were activists, and some came spoiling for a fight. A CBS-TV poll found that only 4 percent of the delegates considered themselves conservatives - the kind of delegates who might have backed John Glenn, Reubin Askew, or Ernest Hollings, who all dropped out of the presidential race in the early primaries.

Mondale aides worked furiously to hold the convention together. Where necessary, as with the platform, they made concessions when the votes were going against them. Otherwise, they stood firm - as on Jackson's efforts to include a plank against runoff primaries in the South - and managed to win.

The result was a platform that was essentially a product of both Mondale and Senator Hart, and which Mondale is said to feel extremely comfortable with. The minority planks that could have crippled his campaign were blocked.

All in all, even a Hart worker such as Prof. Thomas Cronin of Colorado College concedes it could have gone much worse for Mondale.

The tears of the losers here are drying. Jackson and Hart promise to work for the ticket. The political wounds, sometimes painful, are beginning to heal.

As political analysts frequently remind us, registered Democrats, for all their problems, remain by far the larger of the two parties (43 percent to 30 percent). If the Mondale-Ferraro team can find the spark to get those Democrats to the polls, the presidential race could be far closer than most pundits or the public expect.