Trump rebounds in White House race; Sanders surprises Clinton

ENDORSEMENTS: ANY ONE BUT TRUMP

Cruz, with enough primary victories to present himself as a viable Trump alternative, won the endorsement of former Republican rival Carly Fiorina on Wednesday and appealed to anti-Trump Republicans to back him.

"If you don't want to see Donald Trump as the nominee, if you don't want to hand the election on a silver platter to Hillary Clinton and the Democrats, then I ask you to join us," Cruz said.

Trump, a former reality TV show host, has peppered his campaign with put-downs of rivals and critics. Many mainstream Republicans have been offended by his statements on Muslims, immigrants and women and alarmed by his threats to international trade deals.

But Cruz, 45, is a hard alternative for some of the mainstream Republican leadership to get behind. A fiscal and social conservative, he is unpopular with fellow senators who were targets of his personal attacks and who blame him for orchestrating a government shutdown in 2013 in a failed attempt to derail President Barack Obama's healthcare reforms.

In January, Graham called a choice between Trump and Cruz like "being shot or poisoned." But the senator softened his tone on Wednesday, saying it had become increasingly clear that "Ted Cruz is the most viable alternative to Donald Trump."

An aide to former Florida Governor Jeb Bush, who dropped out of the race last month, said Bush would meet with Cruz, fellow Floridian Rubio, and Kasich, governor of Ohio, in Miami before the March 15 contests. It was not clear if he planned to make an endorsement.

Clinton, 68, won in Mississippi, but the victory in Michigan by her opponent from Vermont was expected to prolong the fight to pick a candidate.

Clinton holds a sizable delegate lead, with 1,221 compared with Sanders' 571. She has been helped by winning Southern states by big margins and keeping most of her losses narrow.

Clinton's campaign has been dogged by questions over her use of a private email server while she was secretary of state and - in a sign the issue will not go away - the Republican National Committee filed a lawsuit on Wednesday seeking emails between Clinton and her aides.

Trump could open a sizable delegate lead if he is able to win next Tuesday in Florida, Ohio, or Illinois, states that allot all their delegates to the winner.

Kasich, 63, of Ohio, and Rubio, 44, of Florida, could throw a wrench into Trump's delegate stash if they win in their home states next week.