Some of Jeb Bush's most steadfast allies think Saturday might be the end. Donors, who poured millions into his campaign and super PAC, have stopped giving – one refusing a direct request to raise $1 million this week. Bush himself is hitting the phones, pleading for patience with his most influential supporters. And even some of his confidants are suddenly dejected after a dispiriting week capped off by South Carolina Governor Nikki Haley rejecting Bush in favor of Marco Rubio. "What a kick in the balls," said one of Bush's closest supporters and one of the more than a dozen...