There's a warning sign embedded in the fundraising totals for Republican presidential candidates.

The second-quarter fundraising deadline passed Saturday night without much to show, with all candidates -- President Joe Biden and Donald Trump included -- posting lower-than-expected totals, reported Politico.

Ron DeSantis' campaign committee posted a higher topline number, $20 million, than Trump's campaign committee, which came in at $17 million, which mostly came from his joint fundraising committee. But the former president eclipses his GOP rivals in small-dollar donations -- at $14.6 million compared to $2.8 million for the Florida governor.

The lack of small-dollar donors is a warning sign for GOP candidates looking ahead at the general election, and while Biden is behind the fundraising pace set by Trump and Barack Obama in their own re-election campaigns, the prospect of a second term for him isn't driving up donations for Republican challengers.

While the president and the Democratic National Committee together have $77 million in cash on hand, individual donations and national party donations are both allowed at much higher amounts than Obama's re-election campaign in 2011, and GOP totals do not reflect money from the Republican National Committee.

Mike Pence may not reach the threshold of 40,000 donors required by the Republican National Committee to be allowed into the first GOP debate, set for Aug. 23 in Milwaukee. And while Republican challengers Nikki Haley, Tim Scott and Chris Christie appear likely to make the cut, their fundraising totals are far behind Trump and DeSantis.