Yet those aren’t even the most troublesome parts of the Florida senator’s most recent campaign finance report. Rubio may be slowly rising in the polls, but his third quarter filing revealed a campaign that’s also out-manned by many of its rivals in the early-voting states. His staff is largely concentrated in Washington, with just a small umbrella of on-the-ground, early-state operatives — and he’s already at a disadvantage because he hasn’t invested the time in early-state visits that some of his opponents have.

For all the recent buzz surrounding his candidacy — fueled by strong debate performances — Rubio isn’t raising enough money to keep pace with his rivals in the top tier and he’s running out of time to assemble a robust field organization.

“If Trump-mania subsides, you’ve got to have a mechanism and a structure,” said Chip Felkel, a South Carolina Republican strategist who isn’t affiliated with any campaign. “I think you’re being risky if you don’t put a structure in place.”

Operatives in early-voting primary states like Iowa and New Hampshire say that underneath the hood, there are some warning signs. Rubio has spent a combined three weeks in Iowa and New Hampshire this year — by comparison, New Jersey Gov. Chris Christie, who badly trails Rubio in the polls, has spent six weeks in New Hampshire alone.