Pick up the phone! Donald Trump is calling.

Donald Trump has begun making house calls.

The Republican presidential front-runner has begun robocalling independent voters in California, urging them to change their party affiliation in time to vote in the June 7 state GOP primary.

The message begins with a familiar appeal, if delivered a bit stiffly: “I need your help to make America great again!”

Trump briefly explains voting rules in California — namely, that those voters without a stated party preference are ineligible to vote in the Republican primary. The candidate instructs voters to go to his website for information about how to change their party affiliation by the May 23 deadline, so they can cast a Republican ballot.

“Time is short and every vote counts,” Trump urges, using his Trumpian sales voice. “I want your votes.”

The automated call is a sign of California’s importance in the nominating process.

For the first time in recent memory, votes cast in the California primary may determine the Republican nominee. Trump is betting heavily — spending as much as $20 million, Politico reports — in California and the other remaining state primaries to secure the nomination ahead of the Republican National Convention.

“If you’re Donald Trump and things go well between April and May, you can clinch the nomination with California,” said Jim Brulte, chairman of the California Republican Party. “If you’re not Donald Trump and things go okay for you, you can deny Donald Trump the nomination by doing well in California.”

Indeed, Trump and his two primary opponents, Texas Sen. Ted Cruz and Ohio Gov. John Kasich, are scheduled to speak at the typically low-key California Republican Party convention, which begins Friday in the Bay Area.

This article originally appeared on Recode.net.