As Clinton’s network of fundraisers in cash-rich regions like Los Angeles and the Bay Area struggle to fill events where tickets typically cost $2,700 — the maximum a donor can give in the primary — Sanders is not holding any. His money comes almost entirely online, and keeps coming and coming, far faster and more steadily than small donations do on Clinton’s website.

Clinton’s rainmakers have grown anxious. She began the year with $10 million more in the bank than Sanders, but that cushion is disappearing fast.

“The pond is getting fished out. Everyone is sending invitations to the same group of people. And those people have already given as much as they are allowed to give,” warned a Clinton loyalist in Los Angeles who has raised tens of thousands of dollars for the campaign.

“There are only so many people in Hollywood with $2,700 to give. Eventually you burn through them,” said another political insider, an advisor to wealthy donors in Los Angeles. Both spoke on condition of anonymity to comment on the fraught issue of cash.