By Nandita Bose, Jarrett Renshaw and Jeff Mason
WASHINGTON (Reuters) - U.S. Vice President Kamala Harris's campaign officials and allies made hundreds of phone calls on Sunday, locking in delegates' support for her presidential nomination ahead of the Democratic National Convention in August while seeking to block any would-be challengers, multiple sources said.
At the same time, Democratic state party chairs held a Sunday afternoon call to discuss backing Harris as the party's nominee. Several participants said Harris has the chairs' full support.
Harris's outreach to delegates started almost immediately after President Joe Biden dropped his reelection bid on Sunday. Locking in their support and the backing of state chairs is essential to ensuring Harris replaces Biden on the Nov. 5 ballot as the party's rival to Republican Donald Trump.
"A lot of people are working on it right now," a source familiar with the matter said. "She has made clear she will work to earn their support," the source said.
The vice president's office and the Harris reelection campaign declined comment. Several leading Democrats endorsed her on Sunday, but powerful former House Speaker Nancy Pelosi and former President Barack Obama were among those notably silent.
About 4,000 Democratic delegates, meeting in Chicago from Aug. 19-22, will pick the Democratic Party's nominee. Most are committed to Biden after state primaries this year. After his abrupt announcement, they are not bound by any law or party rules to back anyone.
Although Biden was the party's presumptive nominee, he has no direct power to choose the delegates' formal nominee.
Harris needs the support of 1,969 of the 3,936 Democratic delegates to secure her nomination at the August convention.
The southern U.S. state of Tennessee became the first to pledge its 70 delegates to the vice president, sources added.
Even before Biden stepped aside, Harris began to emerge as the consensus pick and in an open nominating process, the vice president will have several advantages that give her a leg up over any potential challenger for the nomination.
Bruce Thompson, a North Carolina attorney and early backer of Harris's failed 2020 presidential bid, said he had been actively calling delegates to get them to support Harris.
Thompson, who is also on the Democrats' powerful rules committee, said he was finding broad support for Harris.
Chip Forrester, co-chair of the southern region finance committee of the Biden-Harris campaign said the Tennessee delegation voted unanimously to support Harris as president.
"Tennessee became the first state in the country to officially unanimously endorse Harris as president," Forrester said.
Asif Mahmood, a Pakistani American doctor, delegate and Democratic fundraiser based in California, said he had personally spoken with 60 delegates and all had agreed to back Harris. "There is a new excitement, a new hope that this can be done," Mahmood told Reuters.
He said he expected Harris to raise $700 million to $1 billion before the Nov. 5 election, and predicted $30 million would be raised in the next 24-48 hours.
Abortion rights groups including Emily's List and Reproductive Freedom for All began reaching out to delegates to make the case also for Harris. The vice president has been the leading voice for abortion rights in the Biden administration.