The Indiana primary, with 57 delegates at stake, stands in the minds of many Republicans as the last major hurdle for Trump. Cruz and his allies have poured every resource and manoeuvre at their disposal into the state in a last-ditch effort to derail Trump.
"They not only put all their chips in the Indiana basket, but they made it very clear how desperate they've become. They have tried everything imaginable," said Pete Seat, a well-connected GOP operative whose firm advised the campaign of Ohio Governor John Kasich, the third Republican left in the race.
On a frenetic final day of campaigning, Cruz faced uncomfortable questions about the viability of his foundering candidacy. Although he held up Indiana as a must-win state, the senator from Texas later argued he could lose and still force a contested party convention and wrest the nomination from Trump in Cleveland.
The last two public polls here showed Trump with double-digit leads over Cruz. Kasich - who brokered a stop-Trump deal with Cruz to bow out of Indiana if Cruz ceded Oregon and New Mexico to Kasich - is running a distant third.
Trump has been buoyed in Indiana by two main forces. First, his populist messages about trade deals that hurt workers and a "rigged" and "corrupt" political system that resonated in a state whose manufacturing economy is hollowing out.
Trump also is benefiting from his newfound aura of inevitability. Nine in 10 Republicans now think Trump will be their party's nominee, according to a new CNN-ORC national poll.
"You cannot underestimate the impact that Trump winning all counties last week in the 'Acela primary' had on Indiana," veteran GOP strategist Scott Reed said, referring to five East Coast primaries that Trump swept. "A month ago, Cruz was leading Trump by 20 per cent in Indiana. Trump's wins, coupled with landing his plane in state, has driven voters into his column."
Cruz came face to face with the forces working against him outside a campaign stop in Marion, where he approached Trump supporters who had been heckling him from across the street with jeers such as "Lyin' Ted" and "Hey, Cruz, do the math".
Cruz approached and engaged the demonstrators. One of them told him, "Indiana don't want you".
"Sir, America is a better country ... " Cruz said, at which point the man interrupted to say: "Without you."
Trump sat down for lunch with two aides and a guest, author Edward Klein, who wrote a series of bombshell books about the Clintons, spreading rumours and innuendo - much of it discredited - about Hillary's health and Bill's sexual adventures. It was unclear what the foursome discussed, but a few hours later in Carmel, Trump gleefully gave his crowd a preview of the Clinton attacks to come.
"Folks, I haven't even started yet," Trump said. "Now I'm going to start focusing on Hillary. It's going to be so easy."
