It is all a myth.
The popular vote tells its own story
Donald Trump has almost as many votes as Cruz and Kasich, his last competitors, put together and over a third more than Cruz.
Trump has 1000 delegates, more than Cruz/Kasich/Rubio combined-needing only another 237 to have a majority for the nominated. Cruz and Kasich are mathematically eliminated.
But the telling factor is in head to head primary battles between Trump and Cruz, not caucuses which can and have been manipulated, the simple fact is that Cruz has won only three.
Cruz won his own state of Texas (where he couldn't crack 50% but Trump got 60% in New York) Oklahoma and Wisconsin-that's it. "One for 37" Kasich has won only his home state of Ohio and also by under 50%.
Of Trump's 25 victories only two, Kentucky and Nevada were caucuses. There is no doubt whatsoever that if they were primaries he would have won them easily. Colorado, whose delegates "were assigned to Cruz" is anyone's guess.
If, as expected Trump wins big in Indiana and California, if the race gets that far after Indiana, makes it obvious Trump will win) his record against Cruz will be so large, clear and indisputable that the myth of Cruz having been competitive at any point will be well and truly buried and his campaign, in the months since Illinois, at least, will be seen as purely that of a spoiler whose only chance was to deny Trump getting a majority.