Cruz is merely taking the next step toward the Presidency in a manner that he previewed when I profiled him for the magazine, in 2014. Cruz may be wrong about Republican and Presidential politics, but he’s consistent, and his rejection of Trump, when every other putative successor as Republican nominee has endorsed him, fits into his master plan. In simple terms, Cruz thinks that conservative Republicans win Presidential elections
… despite his defeat, Cruz positioned himself perfectly to reassert his core argument in 2020. Assuming that Trump loses this year, Cruz can argue that Trump failed because he did not fully embrace conservative dogma. While Trump has taken conservative positions during the campaign, he has held a variety of less hard-line views over the years, including on such bedrock issues as abortion.
And Trump has, in any event, largely steered away from social issues during his campaign. In recent days, Trump even appears to be trying to moderate his views on illegal immigration, which had been the heart of his conservative appeal. The greater Hillary Clinton’s margin of victory turns out to be, the stronger Cruz’s claim will be. Without a political base of his own, a defeated Trump will be a deserted Trump; he will not be making a second run for President in his mid-seventies. Trump will be a scorned and discredited figure.
… Cruz has built his career on repudiation of moderation—and on confrontation with his fellow-Republicans. On balance, it has worked out well for him. As a first-term senator, he nearly shut down the federal government single-handedly in a failed bid to end Obamacare. This kind of absolutism alienated his Senate colleagues, including Republicans, but it propelled him to a strong second-place finish in the Republican Presidential primaries—an extraordinary achievement for a politician who has won exactly one election in his life. For a party picking up the pieces after a catastrophic Presidential election (if that’s what it turns out to be), there will be great appeal in a politician, like Cruz, who can say, “I told you so.”