CHICAGO (AP) - Marco Rubio's "lean" presidential campaign is putting on weight.
By every measure, the Florida senator's bid for the Republican nomination has grown more robust in October, boosted again by a strong showing in Wednesday night's debate. In preference polls and money flowing in, he's ticking upward.
The campaign's fundraising, which lagged that of several competitors over the summer and early fall, just finished its best month yet. In the hours around the debate Rubio raised $750,000 online - more than on any previous occasion.
The next day, Rubio was cheered at two fundraisers in Chicago, each of which had more attendees than organizers had planned. At a "young professionals" happy hour at a downtown sports bar, the 44-year-old Rubio told a rowdy group that he woke up that morning "still kind of wired" from the debate.
"It's becoming easier to get people to say yes," said Chris Grozev, who said he sold a couple hundred $100 tickets to the happy hour.
Phil Rosen, a New York real estate lawyer who hosted one of the most lucrative fundraisers for the campaign a few weeks ago, said he's since had "people come out of the woodwork and call me directly, asking for another event so that they can meet him."
Donor enthusiasm has given campaign leaders who have prided themselves on a slim and sleek operation - partly out of necessity because of low cash flow - the confidence to increase hiring.
The staff grew by about one-third in October, making for crowded conditions in the Washington row house that serves as headquarters. Rubio is steadily adding resources in each of the first four voting states, and the campaign just signed an office lease in South Carolina, the third state voting in the primaries early next year. Volunteers there had been working out of a garage.
"We're definitely building," said Terry Sullivan, Rubio's campaign manager. "But we're scaling at the right time."
With growth comes the potential for growing pains.
Rubio's competitors are sharpening their criticism of the freshman senator.
In Wednesday's debate, mentor-turned-rival Jeb Bush went after him for missing Senate votes while he campaigned for president.
"You can campaign, or just resign and let someone else take the job," Bush jabbed. The former Florida governor came to the debate after briefing his top fundraisers on a strategy that hinges on overpowering Rubio, whom his campaign sees as his most dangerous competitor for the voters and donors who want to see a traditional nominee.
Rubio had a retort at the ready, pointing out that Bush hadn't raised similar complaints about senators who'd missed votes to campaign in previous elections.