WASHINGTON — Two past Joe Biden black supporters in South Carolina are switching their allegiance to Rep. Tim Ryan, suggesting the former vice president has not consolidated his support in a state central to his 2020 plans.

Fletcher Smith and Brandon Brown, who played senior roles in Biden's last presidential campaign in 2008, attended a meeting Biden held last month with a small group of African American leaders in Columbia and both told NBC News that he's neglected some relationships in the state.

Biden has consistently lead polls of black voters by wide margins, providing him a crucial foundation of support in the 2020 primary where as many as 1 in 5 voters in next year's primary contests are expected to be black. In South Carolina, African Americans are even more important, since they make up a majority of the Democratic electorate.

Smith, a former state representative, served as South Carolina co-chair for Biden's 2008 campaign and Brown served as the deputy political director. And when Brown ran unsuccessfully for Congress last year, Biden endorsed him by saying, "I have known Brandon for a long time and have seen firsthand Brandon's ability to lead and desire to serve."

But both are set to this weekend to endorse Ryan at events in South Carolina, where the far less well-known Ohio moderate has been quietly working to chip away support from rivals like Biden, who currently holds a large lead in the Palmetto State, according to polls.

Rep. Tim Ryan, D-Ohio, launches his campaign as Democratic presidential candidate at a rally in Youngstown, Ohio, on April 6, 2019. Aaron Josefczyk / Reuters

"This is one of the toughest decisions," Brown said, noting he has a long history with the Biden family and he has attended parties at the vice president's home. "What you're seeing is almost like a changing of the guard."

Smith and Brown are political moderates who say they still admire Biden, but are looking for someone new who can also appeal to centrists and win the Midwest against President Donald Trump.

Brown, who runs an annual football classic among historically black colleges and universities, said that Ryan, who was recruited to play football in college, has been supportive of HBCUs from his spot on the House Appropriations Committee.

"Congressman Ryan reached out to me and said, 'Hey I want to meet with you,' and actually spent time with me. We developed a friendship, and I introduced him to some people and you could immediately see he resonated," he said. "We see that Tim Ryan represents those traditional values that in South Carolina still hold true. He is not a socialist — that resonates in South Carolina."

The pair said their decision had nothing to do with the controversy over Biden's recent comments about working with segregationist senators, nor his conflict with Sen. Kamala Harris, D-Calif., over busing, which both dismissed as nonissues.

Smith, a lawyer who served in the state Legislature for a dozen years, said, "I love the vice president, but at the same time I'm looking for a new voice from a new generation whom the torch needs to be passed to. I think we need a candidate who can still talk to people in the Midwest as well as working-class people and middle-class people."

And he said the Biden campaign hadn’t done enough to woo back longtime supporters like him.

"I have a basic standard: If you call me early enough and ask for my support, then I'll give you good consideration. If you don't call me, then I'll assume you don't need my support. I didn't get that call this time," he said. "I think his campaign decided we don't need the old heads, there are a lot of young bucks out there."

Biden's campaign, which did not comment for the record, noted that both men got almost two hours of facetime with the former vice president during last month’s meeting in Columbia and said they had received calls from the campaign.

Brad Bauman, a senior adviser to Ryan's campaign, said Ryan is a natural alternative choice for Biden supporters.

"South Carolina voters are looking for answers that address the fear and anxiety of the Trump era, but also a candidate who understands that going back to the way things were before Trump isn't the answer," Bauman said. "Congressman Ryan’s message of transforming the broken systems, especially the economic stress, that led America to this moment is resonating with folks across the state who are saying it’s time we break from the past."

Ryan and Biden will not appear on stage together at next week’s debate in Detroit, since Ryan will debate on Tuesday and Biden on Wednesday.

Biden has long maintained deep ties to South Carolina, where a majority of Democratic voters are African American, and the state is seen as a linchpin of his path to securing the 2020 Democratic presidential nomination.