He has to become more aggressive. He's getting crushed.
Cruz has a plan, which does not include taking Trump on head to head at this point. Right now, he is playing the long game. He has a better ground game in most of the early states up to and including the SEC primary in March. He plans to build up his pool of delegates in all of the proportional states, and continue to reach out to the supporters of other candidates so that they become Cruz supporters when their candidates drop out. And with Cruz's fundraising and grassroots support, he will be able to last long into the primary season, a lot longer than almost anyone other than Donald. So at some point, it may become a 2 man race, but it's not there yet, and Cruz is not going to treat it like it is.