In her first conversation with Rep. Bobby Rush, a veteran member of the Congressional Black Caucus, Harris was explicit about what she wanted: his endorsement in the Democratic presidential primary. Rush demurred, not yet ready to pick a side in the most crowded Democratic race in modern political history.

Still, Rush was impressed with Harris and watched her closely in last week’s debate. When she called again after the face-off, the Illinois congressman said he was ready to back her campaign.

Harris’ courting of Rush is a snapshot of the broader, behind-the-scenes effort underway to win over the 55 members of the CBC — a primary-within-the-primary for support of the nation’s most influential black lawmakers. It reflects both the increasing power of black leaders within the Democratic Party and the importance of the communities they represent to those jostling to become the party’s White House nominee.

It also puts the CBC in the awkward position of having to choose between some of its own members — New Jersey Sen. Cory Booker and Harris, a California senator — and other longtime allies of the influential caucus, including former Vice President Joe Biden.

“It is beautifully uncomfortable to be in this spot,” said Rep. Emanuel Cleaver, D-Mo., who’s received calls for support since the debates from two top-tier candidates. It’s a departure, Cleaver said, from the years when “the CBC members had one choice and it was the person who had strong civil rights credentials.”

With seven months to go before the first primary votes are cast, most CBC members are still undecided, including powerful and influential lawmakers like Financial Services Committee Chairwoman Maxine Waters of California, House Oversight Chairman Elijah Cummings of Maryland, Majority Whip James Clyburn of South Carolina and civil rights icon John Lewis of Georgia.

Those who have endorsed candidates have split chiefly between two: Harris and Biden, who has deep ties to the African American community. As of Wednesday, Harris had seven endorsements from CBC members and Biden had five. Booker had the backing of two CBC members from his home state of New Jersey.

Harris, Biden and others have been wooing CBC members through formal phone calls and in-person meetings, as well as casual conversation in the halls of Congress, according to interviews with lawmakers and their allies. Biden met with the CBC members on June 20 to discuss criminal justice policies. Harris and Booker have both attended some of the weekly CBC meetings in the Capitol.

Questions of electability and loyalty are driving the CBC members’ decisions.

Harris has seen an uptick in CBC support since the debate, when she challenged Biden over his comments about working with segregationists and his opposition to busing, noting her own experience as a child who was bused as part of desegregation efforts.

“In that moment, I knew exactly what she was talking about — she was talking about access to opportunity that would otherwise change the trajectory of her life,” Rep. Jahana Hayes, a freshman CBC member from Connecticut, wrote in her endorsement Wednesday. “That resonated with me. That was me.”

Rush said the moment stood out to him as an example of how Harris might take on President Donald Trump in a general election debate. He concluded: “She is electable.”

The split in the CBC thus far between Harris and Biden roughly reflects the divide among voters.

Biden remains atop the field of Democratic candidates in several post-debate polls, but Harris enjoyed an increase in support from voters. Among black Democratic voters in particular, support for Biden and Harris is roughly equal in a Quinnipiac poll following the debates, 31% and 27%, respectively.

But Democrats, including African American Democrats, are still most likely to call Biden the contender best suited to defeat Trump. The Quinnipiac poll found 42% of Democratic voters, and 53% of black Democratic voters, saying Biden had the best chance to beat Trump of the two dozen or so candidates.