The billionaire Tom Steyer has qualified for Tuesday night’s Democratic debate in Charleston, South Carolina, ahead of the state’s primary next weekend.

The news may concern Joe Biden.

The former vice-president is seeking victory in the first southern state to vote, in order to establish himself as the moderate alternative to Bernie Sanders, the progressive Vermont senator who won Nevada on Saturday.

Biden finished a distant second as Sanders performed strongly with minority voters. Nonetheless the former VP’s campaign manager, Greg Schultz, tweeted: “Make no mistake: the Biden comeback starts tonight.”

In an interview broadcast on CBS’s Face the Nation on Sunday, Biden said a recent fall in his support with African Americans in South Carolina, a key bloc for a man who won elections with Barack Obama in 2008 and 2012, was due to “Steyer spending hundreds of millions, tens of thousands of dollars, millions of dollars, out campaigning there.

“And so I think a lot is happening in terms of the amount of money being spent by the billionaires to try to cut into the African American vote. I think that has a lot to do with it.”

Biden denied that Steyer was melting his “firewall” and expressed confidence in his chances.

Steyer also spent heavily in Nevada but failed to qualify for its debate. On Sunday, with results still coming in, he was in a close contest for fifth place with Amy Klobuchar, a senator from Minnesota.

Former South Bend, Indiana, mayor Pete Buttigieg – whose campaign formally queried the Nevada results after placing third – Massachusetts senator Elizabeth Warren and former New York mayor Mike Bloomberg will also debate in South Carolina.

Bloomberg, another billionaire, is not competing in South Carolina, focusing instead on Super Tuesday, 3 March, when a host of states will vote.

The Hawaii congresswoman Tulsi Gabbard is the only candidate left in the race who has not yet qualified for the South Carolina debate. The deadline for meeting poll-based qualifications set by the Democratic National Committee is Monday.

On Twitter, Steyer said he was “proud of everything we accomplished in Nevada. We’re only gaining strength as the electorate gets more diverse and more representative of the country.”

In South Carolina, Steyer has campaigned heavily and focused on issues important to black voters including support for historically black colleges and universities and reparations for slavery.

Speaking to the Guardian this week, one South Carolina voter, Najeema Davis Washington, said Steyer “caught [her] attention years ago” with his advocacy for combating climate change and the racial wealth gap, issues she said “speak to what affects African Americans most”.

But the realclearpolitics.com polling average still puts Biden top in South Carolina with 24.5% support – followed by Sanders on 21.5% and Steyer on 16.5% – and many in the state still expect a Biden win.

Antjuan Seawright, a Columbia-based Democratic strategist, said: “This is a trust election and voters will want to go with who they know. And they know Joe. Joe has been there for the people of South Carolina and he will be rewarded by the people being there for him.”

On Sunday at a black church in North Charleston, Biden said the 2020 election could rip out the roots of systemic racism, if voters help him win the nomination and beat Donald Trump.

Speaking from the pulpit of Royal Missionary Baptist Church, Biden drew an ovation with a reference to a racist governor of Alabama who ran for president in 1968 and 1972.

Trump, Biden said, “is more George Wallace than George Washington”.