What’s most important, though, is a candidate’s burn rate — that is, how much a campaign has spent relative to its fund-raising. Too high a burn rate can spell trouble for the long haul.

Former Representative John Delaney of Maryland, for instance, had a burn rate of more than 750 percent in the second quarter. Senator Kirsten Gillibrand, whose campaign has a large staff, had a burn rate of 185 percent. Mr. Hickenlooper was at 142 percent. Representative Tulsi Gabbard of Hawaii had a burn rate of 121 percent.

On the other hand, some campaigns that have not raised much money have managed to keep costs down. Senator Michael Bennet of Colorado, for example, had a burn rate of 47 percent. Mr. de Blasio’s was 33 percent and Mr. Bullock’s was 28 percent. While they have failed to catch fire, these candidates could see no real reason to drop out just yet.

And many face a steep climb in the polls

In a Quinnipiac University national poll released Monday, 14 presidential candidates did not even register 1 percent support, while four others earned 1 percent each. It was a stark reminder of just how long the odds are for the vast majority of the field.

After two debates, none of the lowest-polling candidates have managed to generate the kind of meaningful, lasting momentum that would allow them to break into the next tier of contenders.

Certainly, there is still time to create a viral moment and to work to capitalize on it, and for some candidates, that dream is enough to prevent them from dropping out in the near future. But that goal grows more elusive every day as the top contenders dominate the spotlight.

“I don’t understand why some of the 1-percenters aren’t leaving the field,” Ms. Hardy said. “We need some people to drop out.”