Flores, a Democrat who served on the Nevada State Assembly, wrote a piece for New York magazine's The Cut on Friday alleging that Biden "inhaled" her hair and then kissed her before a campaign rally in 2014, when she was running for Nevada's lieutenant governor.
"He proceeded to plant a big slow kiss on the back of my head," Flores wrote. "My brain couldn't process what was happening. I was embarrassed. I was shocked. I was confused...I wanted nothing more than to get Biden away from me."
She called the alleged incident "demeaning and disrespectful."
A spokesman for Biden had said in a previous statement that neither Biden nor his staff at the time recalled the incident Flores described.
Henry R. Munoz, the Latino Victory Project co-founder who organized the 2014 campaign event, said on Sunday that thorough review of the rally appeared to show that Biden and Flores were never alone together. "These are both individuals that I love and respect, and who have been supported by and who have supported the organization I co-founded to lift Latinx candidates," Munoz said in a statement. "Yet at no time were these two leaders alone together and I, and the organization I cofounded and those in attendance, do not believe that circumstances support allegations that such an event took place."
Flores did not explicitly say in her accusation that she and Biden were alone. She said the alleged incident happened after she and other speakers "were ushered to the side of the stage where we were lined up by order of introduction." In an interview with CNN's "State of the Union" Sunday, Flores said the alleged touching "occurred in the chaos of a rally," while the actress Eva Longoria was in front of her. Longoria has not commented about the accusation.
Biden has been gearing for a potential presidential run, and has led early polls of Democratic candidates for 2020. Several declared 2020 candidates, including Sen. Elizabeth Warren, Sen. Amy Klobuchar and Rep. Joaquin Castro, said they believed Flores' accusation. Sen. Bernie Sanders, I-Vermont, who is also running for president, told CBS' "Face The Nation" Sunday he has "no reason to not believe" Flores.
Flores endorsed Sanders in the 2016 presidential race, but said on Twitter Saturday that she hasn't endorsed any candidate for 2020.
Flores told CNN she believes Biden's alleged behavior is "disqualifying" for a 2020 run. "I find a lot of his background problematic," she said.
Biden was already facing heat for his handling of Anita Hill's sexual harassment accusations against Clarence Thomas, who was then a nominee for the Supreme Court. Biden chaired the Senate Judiciary Committee in 1991 when Hill testified, and he said an FBI investigation was inconclusive.
Biden last week said he regretted how Hill was treated. "She was abused through the hearing," he said. "She was taken advantage of. Her reputation was attacked. I wish I could've done something."
