CHARLESTON, S.C. — As Democrats begin to lose patience with the size of their 2020 presidential primary field, one candidate could be poised to seize attention with an unexpected finish Saturday.

Tom Steyer, the California activist billionaire who has largely been a nonfactor in the primary campaign so far, is on track to finish in the top three in South Carolina's contest, according to recent polls, potentially depriving former Vice President Joe Biden of the strong finish he needs to reclaim momentum.

Many Democrats eyeing the general election are eager for underperforming candidates to get out of the way, but few have provoked more annoyance than Steyer, who has invested particularly heavily in South Carolina, with a focus on racial justice and climate issues.

"A lot of Democrats feel as though it's time for Steyer to get out," longtime Democratic operative Karen Finney said. "There's a real frustration that his money could be spent helping us win because it's pretty obvious to most people that there's just not a path for him. And Democrats are becoming increasingly anxious that it's time to start coalescing."

But despite being one of the Democratic Party's single biggest donors in recent elections, Steyer has a long history of going his own way. For instance, he spent millions pushing for President Donald Trump's impeachment over the vocal objections of House Speaker Nancy Pelosi.

In an interview with NBC News on Wednesday, Steyer said he doesn't much care what "the Democratic establishment" thinks about his strategy and called the idea that he's a spoiler for Biden "a crazy statement."

"I mean, he is the Democratic establishment, right?" Steyer said of Biden. "That's an interesting idea if you think you actually own votes. I thought that people got to make up their own minds, but apparently not."

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But Steyer's gains could very well be Biden's losses (and vice versa). The two men are the only candidates who do better with black voters than they do with white voters in South Carolina, according to a recent NBC News/Marist poll. Steyer, who has spent $20 million on television and radio ads here, captures about 1 in 5 black voters in the state, which he attributes to his strong racial justice platform and especially to being the only candidate in the field who supports slavery reparations.

Joe Biden, Tom Steyer and Amy Klobuchar during the Democratic presidential debate in Charleston, South Carolina, on Tuesday, Feb. 25, 2020. Win McNamee / Getty Images

Some moderates are even convinced Steyer is secretly a proxy for Sen. Bernie Sanders, I-Vt. But Steyer, while being a vocal progressive, is running TV ads in South Carolina saying "Bernie's socialist plans won't beat Trump."

Steyer said his motivations are simpler: He thinks he'd make a good president.

"I'm not saying these things so I can get a job. I want to get a job so I can do these things," he said.

He acknowledges the path to get there is more than a little tricky, but it goes something like this: do well in South Carolina, proving he has support among black voters, then use that as a springboard to win delegates next week on Super Tuesday in states such as California and Texas, where he has had people on the ground and TV ads on the air for weeks.

He's then banking on other candidates' dropping out as their money dries up so he can press his financial advantage in a smaller field in which he'll argue that, between Sanders and former New York Mayor Mike Bloomberg, he's the Goldilocks candidate.

As he put it at a breakfast hosted by the Rev. Al Sharpton's National Action Network on Wednesday morning, he's not a "socialist who wants the government to take over big parts of the economy" nor "the Republican mayor of New York City."

Steyer has focused on South Carolina from his first day in the race and has been accused here of buying support by putting local elected officials and activists on his payroll and offering to pay for renovations to a black church via his foundation.

But Trav Robertson, the chairman of the South Carolina Democratic Party, who is neutral in the primary, noted that Steyer and his wife have for 15 years helped provide access to capital for minority-owned banks, including the largest one in the state.

"So I think that it is really understating his involvement in communities of color across South Carolina and the country just to say, 'Oh, this is a rich guy buying his way in,'" Robertson said.

The South Carolina focus has made Steyer a threat to Biden, who aggressively attacked Steyer for the first time Tuesday night by noting that the former hedge fund manager invested in private prison companies.

But Rep. Cedric Richmond of Louisiana, a former chairman of the Congressional Black Caucus who supports Biden, wouldn't go so far as to tell Steyer he should drop out.

"I'm not in the life coaching business," Richmond said.