Former President Barack Obama has been in regular touch with Vice President Kamala Harris‘s campaign about a possible endorsement, a source familiar confirmed to the Washington Examiner.

Obama remains the most important Democrat holding out on endorsing Harris since President Joe Biden announced he was suspending his reelection campaign Sunday. In Obama’s statement following Biden’s surprise suspension, he did not mention the vice president.

However, Obama, who has known Harris for more than 20 years, thinks the vice president is off to an impressive start, the source told the Washington Examiner.