Cruz “has been important in giving voice to the [Gang of Eight] opposition,” says Matt Mackowiak, a Texas-based Republican consultant, though he “hasn’t demonstrated the same level of aggressive national leadership on this as he has on a couple other things” — such as his opposition to gun-control legislation and the Obama administration’s drone policy.

One Republican aide suggests, “He’s been as strongly opposed as any member. But whenever you see someone like Ted Cruz not going full throttle, it makes you wonder why.”

In part, this is probably because immigration reform is a tricky and politically sensitive issue, particularly now, when many Republicans think giving legal status to unlawful immigrants is a necessary step in the party’s return to power. One GOP aide who opposes the bill says, “The impression they don’t want to leave is that they’re anti-reform.” Republicans are wary of coming out against the bill when the party establishment seems to favor it generally, he says, and “nobody wants to be the tip of the spear.”