Cruz doesn't have a majority of voters.
No candidate has a majority of voters, including Trump. That is why we are having this discussion. If any candidate had been able to muster a majority of voters then he would have locked in the nomination by now. Now it is only a question of whether any of the candidates will be able to win a majority of delegates without a majority of voters.
If no candidate wins a majority of delegates by the convention, then the nomination will go to whichever one of the candidates (without a majority of voters) who is able to win a majority of the delegates over from the other candidates (also without a majority of voters).
Trump supporters keep arguing that as long as Trump goes into the convention with a plurality delegate lead (no mater how small of a plurality it may be at the time) then it will be stealing the election if the delegates pledged to all of the other candidates do not immediately pledge their fealty to Trump.
So what if Cruz manages to take a plurality lead away from Trump before the convention? Will it be stealing the election if the delegates pledge to all of the other candidates do not immediately pledge their fealty to Cruz? Of course not! Well guess what? The same thing applies to Trump.