Indiana governor Mike Pence backs Ted Cruz
The Indiana governor has backed Republican presidential candidate Ted Cruz, four days before a crucial primary contest there.
Campaigning on Friday, Mr Cruz praised Governor Mike Pence, saying he would enthusiastically welcome his support.
Indiana's primary on Tuesday is the Texas senator's best chance to stem the momentum of Republican front-runner Donald Trump.
Mr Trump has won a string of states, taking him closer to being the nominee.
But if he does not win 1,237 delegates, there will be a contested Republican convention in July.
This would mean the delegates - local party activists and senior Republican officials - being free to pick an alternative candidate like Mr Cruz or the third candidate John Kasich.
It has been an eventful week for the Texas senator, taking a beating in five state primaries, picking Carly Fiorina as his running mate and then being called "Lucifer" by ex-House Speaker John Boehner.
Mr Pence made his announcement on radio on Friday, saying Mr Cruz was the best conservative among "three good men".
Will this matter? Anthony Zurcher, BBC News, Washington
With Governor Mike Pence endorsing Ted Cruz, the #NeverTrump movement takes a step closer to following a "Wisconsin blueprint" they hope will sink Donald Trump in Indiana and disrupt what has been his increasingly steady march to the Republican presidential nomination.
Mr Cruz's double-digit victory in Wisconsin earlier this month was fuelled by a confluence of factors - massive outside advertising spending, a determined ground game by the candidate's campaign team, the support of a popular governor and a local conservative media that was ferociously anti-Trump.
Although the media are much more divided in the Hoosier State -the biggest paper offered a tepid endorsement of Ohio Governor John Kasich, who isn't even campaigning there - the other pieces are falling into place.
Hundreds of thousands of dollars are being spent by the Cruz campaign and outside groups to take down the Republican front-runner, and Mr Cruz has essentially been criss-crossing Indiana for more than week.
Mr Pence had been under extraordinary pressure to get off the fence in the race - and now he has. The endorsement lacked enthusiasm, however - unlike the full-throated efforts of Wisconsin's Scott Walker. It's still good news for Mr Cruz, but will it be enough?
Who's supporting who in Indiana?
TRUMP: Bobby Knight
Former head coach of the Indiana Hoosiers basketball team
"There has never been a presidential candidate prepared to the length that this man is. I think the most important thing in the world is that we vote for the best man for the job, and you've already met him"
KASICH: Indianapolis Star
Indiana's largest newspaper
"Ohio Governor John Kasich offers the best choice for voters in the Republican primaries. Kasich built a solid record as a member of Congress and has led well as Ohio's chief executive."
TRUMP: Mike Tyson
Former professional boxer who served prison time in Indiana for rape
"He's an underdog and no-one likes that he's winning but I know Trump. This is a good thing." Mr Trump boasted about Tyson's endorsement while campaigning in the state.