One night last February, President Obama was attending a million-dollar fundraiser in Florida when he spotted a local Republican activist he knew was close to Marco Rubio, the star Republican senator from that state. At the time, Mr. Rubio was being discussed as a potential vice presidential pick. Mr. Obama approached the woman and asked, “So, is your boy going to go for it?” “The woman certainly wasn’t expecting this sort of welcome,” Politico reporter Glenn Thrush relates in his new e-book, “Obama’s Last Stand.” “But she had seen this side of Obama before, the puckish trash-talker — not the...