The battle between Donald Trump and Ted Cruz has finally begun. A few thoughts on this long-anticipated fight:

(1) The timing is noteworthy. Whereas other candidates—above all Jeb Bush—have been trying, with limited success, to hit Trump for some time, Cruz has held back. Here’s why: The decision-making process of primary and caucus voters must dictate the timing; they are only now beginning to engage, so now is the time that attacks can really influence the outcome.