Cindy McCain, John McCain's widow, is expected to endorse Joe Biden for president. PHOENIX - Cindy McCain, the widow of Republican Senator and the GOP's 2008 nominee John McCain, has endorsed Democrat Joe Biden for president in a rebuke of President Donald Trump by the widow of the Republican Party’s 2008 nominee.Trump has had a fraught relationship with John McCain’s family since he disparaged the Arizona senator during the 2016 campaign.