Ohio Governor John Kasich has exited the US presidential race after struggling to gain traction against Republican front-runner Donald Trump
Ohio Governor John Kasich has ended his campaign for the Republican presidential nomination, leaving Donald Trump as the only remaining candidate.
The billionaire outsider was declared the GOP's presumptive nominee on Tuesday after a resounding primary victory in Indiana that prompted his closest rival Ted Cruz to suspend his campaign.
Over the past seven months, Trump has slowly seen more than a dozen of his Republican rivals step aside.
Rick Perry was first to bow out last September followed by Scott Walker, Bobby Jindal, Lindsey Graham, George Pataki, Mike Huckabee, Rand Paul, Rick Santorum, Carly Fiorina, Chris Christie, Jim Gilmore, Jeb Bush, Ben Carson, Marco Rubio and Ted Cruz.
Even as the field dwindled, Kasich struggled to connect with Republican voters during the often contentious campaign.
The 63-year-old former congressman managed just one primary win in his home state of Ohio, but the lack of victories did not deter him for staying in the race despite growing calls for him to quit.
Kasich painted himself as the only Republican candidate who could defeat Hillary Clinton in a general election, and set his sights on a contested convention, where he hoped to surpass Trump at the last moment.
But an unlikely alliance with Cruz, in which the two sought to slow the property mogul's momentum, failed to yield results for either candidate.
Kasich managed just 153 delegates, putting him fourth overall behind Mr Trump, Mr Cruz and Mr Rubio, who left the race in mid-March.
Some 1,237 delegates are needed to secure the Republican nomination.
Mr Trump has pocketed 1,047 delegates so far, with several states to go before the party's convention in Cleveland.
His likely opponent will be Democratic front-runner Hillary Clinton, who lost the Indiana primary to Bernie Sanders.