Ms. Bass has also waged a previously undisclosed campaign to woo influential liberal leaders, telephoning union presidents to seek their counsel and support. House Speaker Nancy Pelosi is close with Ms. Bass, whom she named to oversee the recent policing reform bill, and has made her admiration clear in private conversations, including with former President Barack Obama. Ms. Pelosi’s aides said she has not conveyed support for any one candidate, is fond of a number of them and, in speaking…