Democratic presidential candidate Tom Steyer has narrowly qualified for next week’s key debate in Iowa after polls in the early voting states of Nevada and South Carolina showed a surprise surge in support.

Steyer, a San Francisco-based billionaire investor whose candidacy has languished in polls near the bottom of a narrowing Democratic field, came in second place with 15% in South Carolina and tied with the Massachusetts senator Elizabeth Warren in third place at 12% in Nevada.

In both polls, conducted by Fox News, Steyer trailed the former vice-president Joe Biden, who stood at 23% in South Carolina and 36% in Nevada.

Steyer qualified for the Iowa debate next week under what is called the early-state polling method where candidates must get 5% support in at least four national or early-state polls, or 7% support in at least two early-state polls.

He will now join Biden, the former Indiana mayor Pete Buttigieg, and the US senators Amy Klobuchar, Sanders and Warren at Drake University in Des Moines, Iowa, on Tuesday for the first debate of the 2020 election year and the the last before voting begins in Iowa.

Self-financing former New York mayor Mike Bloomberg will not make the stage. Under Democratic party rules, candidates must show, in addition to polling support, at least 225,000 unique donors across a minimum of 20 states. The New Jersey senator Cory Booker is also ruled out after failing to meet the polling threshold.

Steyer, who is running on platform that places emphasis on the climate crisis, has barely risen above the low single digits in previous polls. But his Fox poll does not appear to be an aberration; a poll by Morning Consult showed Steyer at 10% combined across four early voting states.

Political pundits pointed to Steyer’s heavy spending in the two states for the surge. According to the Los Angeles Times, Steyer spent $47m during the first three months of his presidential bid, making his campaign one of the largest self-funding political candidates in American history.

“I don’t think these Steyer numbers are a mistake,” the NBC political correspondent Steve Kornacki said on Twitter. “Remember, we’ve had basically no polling out of NV and SC and for months now he’s been spending a fortune in both while the other candidates focus on IA and NH. He’s had the run of the place.”