Over the course of a recent campaign swing in New Hampshire, Marco Rubio was repeatedly asked about campaign finance. His answer each time: “When the media stops charging for ads, I’ll stop fundraising.” 

In late June, the Florida senator’s campaign was the first to make ad buys, reserving $17 million worth of airtime in early primary and caucus states. But he may have bitten off more than he could chew: last quarter’s fundraising numbers show Rubio only has $11 million in cash on hand. 

John Geer, a political science professor at Vanderbilt University who specializes in political advertising, explained the Rubio campaign may have a contract that will allow it to ‘pay as it goes’. But in terms of optics, he said, this doesn’t look good. 

"It’s just telling you that their own fundraising success has not met their own expectations,” said Geer. 

Others see things differently. Stuart Stevens, a political consultant who worked on both the Bush and Romney campaigns, insists Rubio's early ad buy is "smart money management." 

Ads can be bought at any time, he explained, but tend to get get more expensive. There are two advantages to reserving ad space early: it is both cheaper and easier to lock down particular air times before other candidates do. Rubio’s ads are set to start next month and air through February, and the campaign will only have to pay for ad space it actually uses (Rubio's campaign hasn't yet spent anything on ads). 

“It’s very typical for campaigns to reserve time in advance and then pay as they go,” Stevens said. 

Other campaigns have not released how much ad space they’ve reserved. 

Rubio’s team says it isn't worried. 

“We are on track to having our best fundraising month so far,” said Alex Conant, the campaign’s communications director, when asked about the ad buys. 

“Marco will have the resources necessary to compete in every state and win the Republican nomination," he said. 

Last week, the Rubio campaign was quick to brag about its cash on hand. 

“Thanks to smart budgeting and fiscal discipline, Marco Rubio for President started October with more money in the bank than Jeb Bush for President and most other campaigns,” read a press release issued by the campaign. 

But Rubio’s $11 million in cash includes $1.2 million that cannot be used unless Rubio wins the nomination, and $3.2 million that was transferred over from his Senate campaign last quarter. 

While the Florida senator has steadily climbed in the national polls (he is now locked in a battle for third place with Jeb Bush and Ted Cruz), his fundraising hasn’t kept up. 

While the Florida senator has steadily climbed in the national polls (he is now locked in a battle for third place with Jeb Bush and Ted Cruz), his fundraising hasn’t kept up. 

Between July 1 and Sept. 30, Rubio raised $5.7 million. That’s half of what Ted Cruz has, and less than Carly Fiorina. Ben Carson, meanwhile, managed to triple Rubio’s number. 

Asked in Las Vegas if his campaign could be doing a better job of fundraising, Rubio said the campaign was right on track. 

“We feel very confident. We have a plan and we’re on target to hit it, so we feel good about it,” he said. 

But Federal Election Commission filings also reveal that $1.2 million of Rubio’s money raised this quarter came from small-dollar donors. That’s 21% of total contributions, down from 23% last quarter (small-dollar donations, meanwhile, make up 60% of Carson’s number this quarter). 

If that doesn’t change, Rubio will have to rely on big-dollar donors and outside groups for his financial survival. 

In fact, the only pro-Rubio ads that have aired to date have been paid for by the Conservative Solutions Project, a dark money group that is not required to disclose its donors. 

Big cash could soon be coming Rubio’s way. 

Last week, Politico reported that Sheldon Adelson, the casino magnate who spent nearly $100 million on the presidential race in 2008, might be close to endorsing Rubio. Rubio is also reportedly on the Koch brothers’ short list (the Kochs plan to spend close to $1 billion in the 2016 election). 

In New Hampshire, voters wanted to know about accountability, but Rubio insists he is accountable only to the voters. 

“When someone supports me, they buy into my agenda, I’m not buying into theirs,” he told them.