evidence: President Joe Biden ended his reelection bid and endorsed Vice President Kamala Harris to succeed him on Sunday. [...] In a follow-up post, Biden praised Harris and urged Democrats to unite behind her. "My very first decision as the party nominee in 2020 was to pick Kamala Harris as my Vice President," Biden wrote. "And it’s been the best decision I’ve made. Today I want to offer my full support and endorsement for Kamala to be the nominee of our party this year." Harris, who was informed of Biden’s decision Sunday, said in a statement that she was "honored to have the President’s endorsement and my intention is to earn and win this nomination." She is spending the day reaching out to lawmakers, outside organizations and donors, and was slated to make up to 200 calls on Sunday alone, a top Democratic source close to her told CNN.