Brit Hume was on Fox News this AM and said that Trump has taken a lot of the wind out of Cruz's sails by being even more outspoken and angry, and that he is appealing to people who are fed up with the establishment GOP. I don't recall if he used the term "tea party" or not.
While it makes for fun TV, I don't think that anger is a really a good emotion for winning elections. I remember an old study that said that usually the more positive candidate has the advantage. (Reagan vs. Carter, Reagan vs. Mondale, Clinton vs. Bush 1, Bush 2 vs. Gore, etc.)
None the less the polls seem to support his theory. Neither Cruz nor Trump are close to having a majority of the GOP support them, they are trying to get to 15% to be in first place. In the last week Trump has surged, pushing Cruz further down in the polls.