With both candidates set to release fundraising totals later this week, small donors have provided the overwhelming majority of the $41 million raised by Sanders through the end of last month — a tally that’s expected to exceed every campaign except Clinton’s. Her campaign pulled in $75 million between mid-April and the end of September. But a much larger percentage came from donors who each gave close to $2,700, which is the maximum that any one donor can contribute for the primary election.

Clinton’s big-money backers contend she could tap into the small-donor fervor behind Sanders and fire up her own base if she displayed more emotion on the debate stage, according to POLITICO interviews with 10 leading donors and fundraisers who work closely with the Clinton campaign. They see her best approach as a tricky balance between reaching out to Sanders’ populist base, while still casting herself as the most electable Democrat ― which means also aggressively rebutting Republican attacks over her private email use.

“There’s a deep hunger for more action and more fire in belly, and lots of worry all the energy is with Bernie,” said a major Clinton bundler in New York. “Everyone is talking about that,” said the bundler. While noting that most major donors still don’t see Sanders as likely to win the Democratic nomination, the bundler added, “Donors are the base, and they like red meat the same way the activist wing of the party does. … Donors and bundlers are all momentum people like everyone else.”