San Francisco — Six-hundred and fifteen days ago, Walter F. Mondale set forth on his quest for the White House. Now, with only one week left before Americans vote, Mr. Mondale is battling discouragement and predictions that he faces a major defeat.
Mondale brushes aside the gloomy talk and the polls that repeatedly show President Reagan pulling farther ahead. Instead, he continues to draw comparisons between this race and President Harry S. Truman's stunning upset in 1948, when the polls were wrong.
On his current swing through the Far West, Mondale seems freshly energized, despite the grim outlook, by the large, cheering, happy crowds that have met him in city after city.
Even so, analysts point to the hard facts that hang over the Mondale campaign:
Polls. The latest CBS/New York Times survey is typical. It shows Mr. Reagan moving to a 56-37 lead, or 19 points. That's up 5 points in two weeks.
Key voters. Mondale aides know he must pick up strength with independent voters if he is to win. Yet the latest surveys show that it is the President who has gained most among this pivotal group in October.
Key states. Mondale conceded over the weekend that he ''must carry California'' to win this election. He was gaining here in September and early October. Yet now Mondale's private polls show Reagan rebuilding his lead.
Issues. Although he has actively campaigned for nearly two years, Mondale has been unable to find the themes he needs to erode Reagan's support. In fact, the popularity of both Reagan and the Republican Party appears on the rise.
It would be easy at this point for the Mondale team to be overwhelmed by the Reagan juggernaut. Says one senior adviser who is traveling with Mondale:
''We know what the polls say. We see what everyone else sees.''
If there are occasional moments of depression, says this adviser, it is Mondale himself who often bucks up his team. The cheering crowds have also helped. Mondale says:
''Nobody who has been with me the past few days and has seen those crowds (and) the intensity of their response ... could help believe that there is something happening in this country. ... And the pollsters are not getting it.''
Mondale disputes the conventional view of what has happened to his campaign. This view holds that Mondale's only significant gains this fall came during the first debate in Louisville. (After the debate, Mondale quickly had the name ''Louisville Slugger'' painted on the front of his campaign plane. The name, of course, refers to the nation's best-known baseball bat.)
Mondale's new-found momentum, however, lasted about as long as a chocolate ice-cream cone in July. After a brief upward blip, the polls showed Mondale leveling off.
Then came the second Reagan-Mondale debate. Reagan did better. The public seemed reassured. Almost at once, Reagan's lead began moving back up toward the 20-percent range, where it had been before the first debate. In a few states, such as New York, where Mondale had narrowed the race, Reagan again moved back to a double-digit lead.
Mondale and his staff contend that the polls are wrong. Further, they argue that two vital things came from the debates.
First, people started listening to Mondale's message.
Second, when voters began listening, Mondale began building strong, deep-rooted support among undecided voters.
Aides now explain that Mondale's sharp, almost personal, criticism of Reagan during the debates had a specific purpose. Mondale was trying to cut through the aura around Reagan, the person, in order to focus national attention on Reagan's stand on the issues.
Mondale now feels he has the nation's attention, and can exploit issues on which he believes Reagan is most vulnerable, such as fairness, the nuclear arms race, and the mixture of church and state.
In addition, there continues to exist within the Mondale team a lingering hope that women voters will somehow save the Democratic ticket.
This is one reason that, beginning this week, the Mondale campaign will take the unusual step of running a national TV ad featuring Ms. Ferraro, not Mondale.
The ad, which says, ''Gerry, you've made us proud,'' is meant to build on the enthusiasm of female voters, thousands of whom often turn out to greet Ms. Ferraro.
Will it work? Even Mondale's closest aides seem to harbor doubts. In an unusually candid interview last week, Mondale's press secretary, Maxine Isaacs, was quoted as saying:
''I don't feel we're going to lose, (but) I think there's some sentiment building. You suddenly look around and you've spent two years with these people, flying around in the middle of the night, arguing. Now the family's about to break up.''