It’s cold up here in Iowa, but Texans, at least, are getting a warm welcome. Yesterday Rick Perry endorsed Ted Cruz’s bid for the Republican nomination, and today the two are on the trail together. Though it’s hard to measure the electoral impact of any given endorsement, this one seems auspicious for our state’s junior senator. As we all know, Perry’s own bid for the Republican nomination never got any traction this time around. But during his brief time on the trail our longtime governor distinguished himself with his focus on substantive issues like Wall Street reform and racial justice, and by showing more moral clarity than any of his rivals after Donald Trump launched his own bid for the nomination. A number of candidates took exception when Trump scoffed at John McCain’s military service and sneered at Fox News anchor Megyn Kelly. Perry was the only one to object to his blanket slander of Mexican immigrants, way back in July: “The fact is that I’ve said very clearly that Donald Trump does not represent the Republican party.”

Cruz took the opposite approach, and it has proven to be politically shrewd. He and Trump are now the leading candidates for the nomination. With less than 150 hours to go before the Iowa caucus, many Republicans have abruptly concluded that Trump, who remains the frontrunner for the nomination in national polls, will be the party’s standard-bearer, and even that he should be. This uptick in mysterious epiphanies has coincided with Cruz’s ascent in Iowa polls, and the two trends seem to be related.

Perry’s endorsement of Cruz, given his principled opposition to Trump, has a moral valence. For those of us who have been following the race for the Republican nomination, that may seem like an irrelevant observation. Sun Tzu, the great military strategist, wrote that by considering seven factors, he could forecast the outcome of any given campaign. The first is as follows: “Which of the two sovereigns is imbued with the Moral law?” Neither Trump nor Cruz, thus far, but Perry’s blessing can’t hurt the latter.

And I’m feeling superstitious about Sun Tzu at the moment, because I brought The Art of War with me to Iowa, and rereading it with reference to Cruz’s presidential campaign has been eye-opening. I had read it years ago, but hadn’t remembered certain specific pieces of advice: “Water shapes its course according to the nature of the ground over which it flows; the soldier works out his victory in relation to the foe whom he is facing.” “In war, practice dissimulation, and you will succeed.” “Be subtle! Be subtle! and use your spies for every kind of business.” “If your opponent is of choleric temper, seek to irritate him. Pretend to be weak, that he may grow arrogant.”

We had planned to publish the Cruz Rules today, but have gotten a bit behind schedule; we’ll aim for tomorrow, with apologies for the delay. But in the interim, I can offer readers a set of Cruz Rules: the ones written by Sun Tzu, some 2,500 years ago.