On 99 percent of U.S. Senate business, Cruz and Dewhurst probably would vote alike. Yet the ultimate Republican epithet, the M-word — “moderate” — has been bandied. Cruz supporters say Dewhurst is one, which is nonsense. Dewhurst rides roping horses that can go from a standing start to 40 mph in two strides, which is about how fast he recites this catechism: Texas is “the most conservative, most pro-growth, most pro-jobs, most pro-life state in the country” and would not tolerate a moderate lieutenant governor. He says he has presided over 51 tax cuts and has slashed $14 billion from the state budget while Congress has been unable to cut $23 billion from a budget 41 times bigger.

Dewhurst counters the M-word accusation by going nuclear. He notes darkly that Cruz is an eloquent speaker and a Harvard lawyer just like you know who. Dewhurst’s long legislative career presents Cruz — as Mitt Romney’s business career presents Barack Obama — with opportunities for histrionic (and synthetic) indignation about this or that vote or compromise. But, then, Cruz’s record as a lawyer has left him vulnerable to similar rhetoric from Dewhurst’s campaign about some Cruz clients who were unsavory (a “judge-bribing felon”) or impolitic (a Chinese tire company).

If Dewhurst wins Tuesday’s runoff, Capitol Hill gets a veteran conservative legislator. If Cruz wins, congressional conservatism’s small but valuable Doesn’t-Play-Well-With-Others Caucus adds a member.