Three governors and a U.S. senator are the top contenders to serve as Vice President Kamala Harris’ running mate if she’s nominated to replace President Joe Biden on the Democratic ticket, the Associated Press reported Monday. Harris scored a key endorsement from Biden when he announced he was dropping his reelection bid Sunday following weeks of pressure prompted by his dismal June 27 debate performance against former President Donald Trump. All of the country’s Democratic governors have since endorsed Harris, as has a majority of Democratic members of Congress, according to a tally by the Ne…