There are two (barely) conceivable paths to the nomination for Cruz. The first would require him to effectively enter into a non-aggression pact with Kasich and Rubio, and campaign only in states he has a reasonable chance to win; the second assumes that the Kasich and Rubio campaigns will collapse in Ohio and Florida, that he will be the last anti-Trump standing, and that he can win a huge percentage of the votes after March 15.
To me, the former scenario is more plausible, but Ted apparently plans to campaign vigorously in Florida, which suggests that he is committed to the latter. Maybe he doubts, based on his unpopularity with the leadership, that he would be the choice of a brokered convention even if he had the second most delegates. Given the amount of firm support that Trump has, even in the face of a hail of negative ads paid for by rich establishment figures, I think he has made the wrong choice.