"From the moment I stepped into this race, I made it clear that the top two priorities of the next DNC chair must be to strengthen state parties and reform the DNC," Buckley said in a statement. "Now, many candidates have spoken about these issues, but Keith's commitment to the states and a transparent and accountable DNC has stood out."
Ellison, in the same statement, said he was glad to have Buckley's support.
"Throughout this race I've heard loud and clear from DNC members that this is a moment to use all our talents to rebuild the party from the grass roots up," Ellison said in the statement. "That is why I am proud to have Ray's support."
Also Saturday, Robert Vinson Brannum, a native Washingtonian and community activist, pulled out of the race and threw his support behind former Secretary of Labor Tom Perez.
"I believe Tom will listen to and hear from all Democrats; reach out and down to all Americans," Brannum said in a statement. "Tom will not walk away from Democrats. He will fight for the dignity and better quality of life for all Democrats and for all Americans."
Perez is considered Ellison's most serious challenger and has also received significant backing, including the support of former Vice President Joe Biden and four governors
Others in the race include the mayor of South Bend, Indiana, Pete Buttigieg; South Carolina Democratic state party chairman Jaime Harrison; Idaho Democratic Party executive director Sally Boynton Brown; Fox News analyst Jehmu Greene; Air Force veteran Sam Ronan; and Wisconsin attorney Peter Peckarsky.
CNN will host a debate
, moderated by CNN's Dana Bash and Chris Cuomo, featuring several candidates on Wednesday.
The DNC leadership election is scheduled for February 25.
CORRECTION: This story has been updated to accurately reflect Ellison's party affiliation.