MANCHESTER, Iowa — Cory Booker says he’s not leaving the presidential race.

But the New Jersey senator is facing questions about his viability. He is almost certain to miss the December Democratic debate after months of failing to move his poll numbers, and with another candidate who seemed to have vast potential, Sen. Kamala Harris (D., Calif.), quitting the contest this week, the questions have come at Booker fast and furious as he races through Iowa.

“No, I’m focused on staying in the race and I’m focused on being on the debate stage and right now people are responding,” Booker said in an interview with The Inquirer here Friday night after speaking to about 80 listeners in a cramped bar basement, eating pizza slices and drinking bottles of Bud Light.

He said Harris’ departure and the possibility that he could also miss the next debate has prompted a surge in support — and he has been raising an alarm about the party’s diverse field being whittled to a group of all-white finalists. Still, his appearances here include stark appeals for aid.

“Right now, we’re just in an urgent sprint," he said in the interview. "We need help. And we’re asking as many people as we can to go to CoryBooker.com, contribute, so we can do what the billionaires in this race are doing.”

Harris said she had run out of money, but she at least enjoyed a stretch when she rose up and got a close look from voters and the media before plummeting. Booker hasn’t even had that moment yet, baffling many of his supporters and some political analysts who wonder why a 50-year-old senator who has tried to appeal to a broad cross section of Democrats hasn’t drawn more interest, especially as many in the party worry that none of their top candidates check all the right boxes. Booker’s polling support has been mired around 2% to 3%, short of the 4% nationally or 6% early-state backing required to appear in the December debate.

But instead of seeing Harris’ departure as an omen, Booker is trying to turn it to his advantage, arguing that it shows the flaws in the criteria set by the national party, and that Democrats can’t afford to sideline all of their candidates of color. Ironically, his plight and that argument have drawn more national media attention than he has often received.

“I’m just going to say it plain: It is a problem that we now have an overall campaign for the 2020 presidency that has more billionaires in it than black people,” Booker said in a Des Moines speech Thursday that launched a four-day blitz through the state.

He pointed to Democrats’ reliance on black voters to win general elections, and their claims to be the party that represents America’s diversity. Despite the party’s starting with a historically large and diverse field, its top four candidates are all white, and three are in their 70s.

Only white candidates have so far qualified for the December debate, though businessman Andrew Yang is close to making it.

Some Democratic voters here suggested that race may play a role in Booker’s struggle to gain traction, but the senator said no when asked if he thought candidates of color were being treated unfairly.

Instead, he said the Democratic National Committee criteria have allowed wealthy billionaires such as Tom Steyer to pump up his poll numbers and qualify for debates with lavish advertising, while giving too little weight to other factors.

“It’s ridiculous for us not to be on the stage when we have some of the highest numbers of organizers and what many people consider one of the top two or three organizations on the ground,” Booker said. “We’re 59 days from the caucus. Let Iowa voters decide, ultimately.”

Booker has met the fund-raising requirements, but not the polling threshold. That set up the latest desperation appeal for his campaign, which in September warned that he was in danger of dropping out of the race if Booker didn’t hit an aggressive fund-raising goal.

The DNC has noted that the debate criteria have long been set and told the New York Times that no one who failed to reach 4% national support by this stage has ever gone on to win the party’s nomination.

Booker has long responded to questions about his campaign by saying he was aiming to peak just before the Iowa caucuses in February, and he pointed to John Kerry, who trailed late in Iowa only to win the state and the party’s 2004 nomination. He said that he has seen a surge of fund-raising since the November debate and that even if he misses December’s the money “will help us to stay in the race.”