Former Republican presidential candidate Carly Fiorina told The Atlantic Thursday that she will vote for Joe Biden over President Trump in the 2020 presidential election, saying that she believes the U.S. needs "real leadership that can unify the country."Why it matters: Fiorina joins other prominent Republicans who have publicly said they will either not vote for Trump's re-election this November or will back Biden.Not voting for Trump:Sen. Mitt Romney (Utah): The party's 2012 presidential nominee said in February that he will not support Trump shortly after he voted to convict the president on one count in his impeachment trial.John Bolton: Trump's former national security adviser said he will not vote for Biden or Trump and hopes that history remembers Trump "as a one-term president."Voting for Biden: Colin Powell: The former secretary of state under George W. Bush and retired four-star general said that he will support Biden because he believes that Trump has "drifted away" from the Constitution.Carly Fiorina: The 2016 presidential candidate said she will support Biden because she believes he is "a person of humility and empathy and character."On the fence: Sen. Lisa Murkowski (Alaska): Murkowski, one of Trump's consistent foils in the Senate, said that she was "struggling" to support the president's re-election after James Mattis, the former defense secretary, issued a public rebuke.Undecided publicly but skeptical, via a New York Times report:George W. Bush: The former president has reportedly decided not to support Trump's re-election, though he's made no public statements to that end.Jeb Bush: The former Florida governor and 2016 presidential candidate is so far reportedly undecided.Cindy McCain: The widow of the late Sen. John McCain (Ariz.) will reportedly vote for Biden, but remains unsure how public to be about it.Worth noting: While former top military leaders like Mattis and John Kelly are technically non-partisan, they both served in Trump's administration and have publicly expressed skepticism about the president's standing ahead of the 2020 election.Mattis said Trump made a "mockery of our Constitution" and called him "the first president in my lifetime who does not try to unite the American people" after the president's response to mass protests in the wake of George Floyd's killing.Kelly, Trump's former chief of staff and homeland security secretary, said he agreed with Mattis' comments.Go deeper: These Senate seats are up for election in 2020