Democratic presidential candidate Bernie Sanders speaking during a campaign event Saturday at the Reno Sparks Convention Center in Nevada. (Evan Vucci / AP)

Monday is a critical day in Bernie Sanders’ historic, insurgent campaign for president. It’s the last day Californians can register to vote in the state’s high-stakes presidential primary.

The Sanders campaign is counting on high voter turnout to win big in the Golden State and five other states in the final Super Tuesday round of primaries June 7. So far, the news is encouraging for the Vermont senator: More than 850,000 new voters have registered for the 2016 California elections.

According to the San Francisco Chronicle, “the newly registered voters are overwhelmingly young people, with 37 percent under 25 and 64 percent 35 or younger.”

That’s even better news for Sanders, whose message of social justice has won him the lion’s share of young voters this primary season. He is counting on high voter turnout to take a convincing victory in delegate-rich California to the Democratic convention in July—where he can argue that he is the candidate with momentum and a better chance than Hillary Clinton to defeat Donald Trump in the Nov. 8 general election.

California gives Sanders a third reason for hope: “NPP” voters—those who register stating no party preference—can ask for the Democratic ballot on election day.