WASHINGTON (AFP) - Wisconsin Governor Scott Walker on Tuesday (March 29) threw his support behind Republican presidential candidate Ted Cruz, boosting the Texas senator's backing from the party's anti-Donald Trump camp.
Walker's endorsement comes a week before a key primary in his state, with front runner Trump and Cruz in a close race.
"It's time that we elect a strong new leader, and I've chosen to endorse Ted Cruz to be the next president of the United States," Walker told local radio WTMJ.
"He is a constitutional conservative," he added, saying Cruz is best positioned to win the Republican nomination and beat Democratic candidate Hillary Clinton in November's general election.
Briefly a front runner for the Republican nomination before being eclipsed by Trump, Walker pulled out of the race in September.
An ultra-conservative Tea Party favourite like Cruz, Walker is the fifth former Republican candidate to rally behind Cruz after Jeb Bush, Carly Fiorina, Lindsey Graham and Rick Perry.
Some have done so under protest, making it clear they were doing so with the sole aim of stopping Trump.
Explaining his reasons for backing Cruz, whom he had publicly disparaged, South Carolina Senator Lindsey Graham said the Texas senator had the advantage of being "not completely crazy".
Asked "What turns you on about Cruz?" on Comedy Central's The Daily Show last week, he said, "He's not Trump".
Polls in Wisconsin show Trump and Cruz running neck and neck ahead of the third remaining Republican candidate, Ohio Governor John Kasich.
Overall, the New York billionaire is well ahead in the race for delegates required for the nomination - 742 to Cruz's 462 and Kasich's 145 - but his rivals are hoping to prevent him from winning the required 1,237 necessary to clinch the nomination ahead of the party's convention in Cleveland in July.
The prospect of a Trump nomination has split the Republican establishment and fuelled speculation about an implosion of the party.
While many party leaders are drumming up heated resistance to Trump, others have rallied to the tycoon, including his former presidential rivals Chris Christie and Ben Carson.
Walker, who has long criticised Trump, said he had timed his endorsement for greatest effect in Wisconsin's primary next Tuesday.
All Republican and Democratic candidates are campaigning in the state ahead of the vote.