On Monday, Joe Trippi figured that to carry California, the embattled Mondale campaign must convert 80,000 California moderates from the leaning-to-Reagan column for every remaining day until Nov. 6.
Very difficult, admitted Mr. Trippi, who is Mondale's California campaign manager and already a veteran at 28 years of age. But, given the size and changeability of the California electorate, he adds, the task is not inconceivable.
As it has turned out, the 13.1 million voters in Ronald Reagan's home state are sitting in front-row seats during this final campaign week.
When both Walter Mondale and Ronald Reagan arrive here next Monday to sum up their campaign cases, the largest political advertizing blitz in the state's history will be roaring at full pitch.
Mondale commercials will be popping onto the television screen at a daily rate that, if sustained for a full week, would result in the average California viewer seeing upwards of 15, says Trippi. And the Reagan campaign is bidding to buy at least as much airtime as the Mondale-Ferraro ticket in every media market in the state, according to longtime Reagan-Bush politico Lyn Nofziger.
For the Reagan campaign, California is a state to take no chances with. The President's political roots are here, and it would be a political embarrassment to lose it. It is also one of three big Sunbelt states, along with Texas and Florida, that the campaign considers crucial for victory in the Electoral College.
For the Mondale campaign, California has offered the best chance the challenger has to break Reagan's lock on those three Sunbelt prizes - the shortest of three long shots. Mondale has been running well behind Reagan here, but less far behind than in Texas and Florida.
Trippi has been framing scenarios since the end of summer for how Mondale could make inroads among moderate voters of both parties sufficient to beard the lion in his den - that is, beat the President in his home state.
The Reagan camp, meanwhile, has been hedging its bets through party-building work - registering voters and building organizations among constituencies outside the Republican mainstream, such as Latinos and college students.
California is, after all, a state where Democrats outnumber Republicans 5 to 3, notes Mr. Nofziger. ''It's a very volatile state,'' he says. ''A lot of people moving in, a lot of people moving out. A lot of change in the makeup.''
And Reagan, he adds, ''hasn't been governor since '74. A lot of people don't remember him.''
Joe Trippi disagrees somewhat. ''I'm of the opinion that the 'undecideds' in this state are different than the undecideds in other states.'' To California voters, he explains, Ronald Reagan is more of a known quantity. Presumably, then , still-wavering voters are not committed to the Reagan they know, and are susceptible to an alternative.
Some Reagan campaign spokesmen see this from the flip side. While they have always expected Reagan's big lead in the polls to narrow as election day approached, they also saw roughly 10 percent of Reagan's margin over Mondale as rock hard - precisely because Reagan is a known quantity here.
Mondale has been fighting an uphill battle here from the start. He lost the California Democratic primary battle to Gary Hart, who - in a reverse of the national situation - was actually better organized than Mondale.
Then, when Mondale pronounced California to be a key target state for his campaign in late August and early September, he was greeted with widespread skepticism from regulars in his own party here. California Democrats are accustomed to having their presidential nominees wring the state for campaign money, then spend it elsewhere.
But in September it was clear that Mondale was serious about California. The Reagan campaign responded immediately by stepping up its own spending here by 50 percent. ''Not that we ever thought we would lose it,'' says Nofziger, ''but we didn't want (Reagan's lead) to close to the point where people panicked.''
The Republicans beat the Democrats in the first stage of the campaign - voter registration. This is traditionally a Democratic weapon, and the party had a banner year, registering 660,000 new Democrats. But the GOP did even better, signing up 720,000 new Republicans.
At one point in mid-September, Mondale trailed Reagan here by 25 percentage points, according to the Mondale campaign's own tracking polls. But the Mondale people decided to stick it out, and the plans seemed to be working nearly on schedule when Reagan's lead dropped to around 9 percentage points the week after the first presidential debate.
''We moved 800,000 voters after the first debate,'' says Trippi.
But after the second debate, the momentum stalled, he says, and a couple hundred thousand voters slipped back to the Reagan column.
One California conundrum is that, according to the latest California Poll by the Field Institute, the same margin of voters that prefers Reagan for President - 10 percent - feels that a Reagan victory should be paired with sending more Democrats than Republicans to Congress.
This could mean, according to poll director Mervin Field, either that Reagan is personally more popular than his policies, or perhaps that the public is keen to balance the power of the presidency.