“People in Super Tuesday states and California, in particular, are not returning their ballots yet,” said Danielle Cendejas, a Democratic strategist in California whose firm did campaign mail for both of Barack Obama’s presidential campaigns. “They’re waiting for a signal, and I think this is a signal. If you were debating between which of the Democrats who aren’t Bernie Sanders or even Elizabeth Warren to throw your hat behind, you’re probably going Joe Biden’s way.”

These “perfect” Democratic voters dropped from 57 percent turnout by this point in 2008 and 62 percent turnout in 2016 to 46 percent turnout so far this year, according to the data compiled and shared by Mitchell, vice president of Political Data Inc. That means Biden, coming off South Carolina, has more room to expand his support before Tuesday.

“If all of these really high-performing Democratic voters had already cast their ballots then it narrows the window that you have to actually make an impact on Monday and Tuesday right before the election,” Mitchell said.

Biden turned in a huge performance in South Carolina, notching his first statewide win in three presidential campaigns and positioning himself to ride the momentum. But in California, Biden is struggling to break double digits in polls and Sanders is the clear frontrunner.

Experts are coalescing around a 10 million figure as the turnout for the presidential primary, up from the roughly 8.5 million in 2016. About 40 percent of Democrats expected to vote have so far turned in ballots. California will award 415 delegates, more than a fifth of the total needed to clinch the nomination.

Biden aides and allies hope to exploit voters’ early hesitations.

Los Angeles Mayor Eric Garcetti, who was campaigning for Biden in Texas on Saturday before returning to California, said the result in South Carolina will “bode very well for Super Tuesday.”

Noting that many voters are “being strategic,” he said, “I think a lot of people who are undecided will break his way.”

Garcetti also suggested that after South Carolina, “I think we can run up our count” of delegates in California. “We’re going to win delegates in California,” he said. “Now the question is how many.”

Recent polls show Sanders averaging a massive 18 percent lead over a second-place Warren, with Biden running in third and averaging 11 percent, according to figures from Real Clear Politics.

Biden has little chance of winning the state. But he needs a big turnaround to help keep Sanders from a runaway delegate lead. For Biden to hit the 15 percent statewide threshold, he would need to approach 18 percent in the remaining vote that comes in.

That will depend on what the others decide to do heading into Super Tuesday. And it will hinge on just how much attention is paid to Biden’s victory this weekend on the Sunday shows and wall-to-wall cable coverage headed into next week.

But Cendejas said the South Carolina result is likely to keep Biden above 15 percent statewide in California.

It “changes the game for sure,” she said.