The problem is all of the other candidates were relative newbies without the kind of "gravitas" to overcome it. Cruz, Rubio, Fiorino, et. al were all relatively unknown. Kasich probably was the one with the most experience, but he was way too liberal for the base. The only big name was Jeb, and well, nobody wants the Bushes anymore, so he was a non-starter.
I had been paying attention to Cruz in the Senate. He'd given a couple of those 'ambush interviews' and came across quite well. I knew others who mentioned him first, so he was known among those paying attention.
Cruz was kept on the defensive from Iowa, and the smear machine never let up. I honestly don't think he was prepared for that so much as debate on the issues. Trump made Cruz' campaign about defending Cruz as much as promoting ideas, and Trump captured an inordinate amount of air time by staying controversial.
While I question such a strategy with a better focused electorate, the sheer and unbridled anger of GOP voters at the MSM, at Congressmen who reneged on the promises they made to get elected and often did not even seem to try to hinder Obama was successfully harnessed by a cult of personality which grew rapidly around Trump. I have little doubt that there were paid operatives on prominent internet forums, twitter, and facebook who worked the crowd to incite that anger and direct it toward anyone but Trump in order to build that cult. That isn't saying all Trump supporters were/are that far in, just enough that any expression of opinion contrary to those worshipful of Trump was met with hostility, harassment, or silenced.
Despite that, the Cruz ground game was solid, and brought him a lot of delegates where Trump didn't even make an effort. Of course, Trump countered that by saying Cruz "stole" those delegates, ever playing the meme that Cruz was using 'dirty tricks', even as Trump slandered him, his wife, and his father with the help of his pal at the National Enquirer and a well trolled internet always hungry for rumor, invective, and scandal. That Cruz did so well against an onslaught unprecedented in the last century of American Politics shows he did quite well, considering he is not the master of self-promotion Trump has made his living being.
Trump successfully harnessed the electorate's anger at poor border security, poor employment prospects, the entire EPA onslaught against American industry (even though Trump said he'd use the EPA to the fullest extent of the law when campaigning in Iowa), unbridled immigration-legal and illegal, especially appealing to xenophobic elements with 'the wall', something Cruz has suggested in 2011, and Trump got the voters to think it was Trump's idea. In fact, many of the ideas Trump put forth (and often walked back) were much the same as the policy points Cruz had had.
The salient difference, unfortunately, is one of character. While I think, given the opportunity, Cruz would have become even better at campaigning, and gone on to defeat Hillary, Trump's history of egregious misbehaviour has become a burden even too great for his cult to bear. Unfortunately, the MSM and the Clintons are using that against Trump, much as the fabricated and fictional misdeeds of Cruz were used against Cruz.
That gambit is simple. Keep the media talking about the sins of the other guy.
Drag out the very real dirt and push that against them.
If Trump had gained that upper hand against the Clintons and used it as effectively as he used it against his Republican opponents, he'd still be in the running. But the Clinton camp has had months to study the strategy, how it worked, why it worked, and remodel it to appeal to not only their base, but the swing votes in the middle, women, and even the religious, and turn it against Trump. That whole time, Trump has either been on the defensive or has been utilizing the same frenzied arguments against the GOP, preoccupied with unconditional loyalty instead of stripping Hillary of the same.
The corner Trump is in leaves him unable to pander to any in the groups he needs to win without alienating his core base of loyal followers. Disillusion those and the election goes to Hillary in a landslide, where otherwise it may be a little closer. Clinton will likely win the majority women's vote, Democrats, of course, blacks, hispanics, gays, and will even attract some blue dog democrats who don't think trump is a good deal. I think third party votes, especially Libertarian Party will be higher than in the past, and I hope the Constitution Party makes progress.
I think the schism in the GOP will not be healed and although I think the party will continue for a couple more cycles at least, if the management stays the same it is on its way to the Elephant's graveyard. That isn't wishful thinking, I had hoped the party could be steered back toward Constitutional Republicaninsm, but the entrenched power elite in the party want no parts of that, as evidenced by the past series of elections, their attitude toward the TEA party faction of the GOP, and toward Conservatives since Goldwater. Ronald Reagan, God Bless him, was a fluke, and the closest we got to a Conservative in the Oval office in a long time. It won't happen again until another Party is ready to move in as the prime contender against the Democrats.