The CBO says: the Senate immigration bill lowers the deficit (see also a nice explainer from pro-immigration analyst Matt Yglesias).
Liberals who support immigration reform have been having fun since yesterday afternoon pointing out that Republicans who oppose immigration are hypocrites because they will surely ignore or dismiss that effect on what is supposedly one of their main priorities. Well, yes -- but I have very little problem with hypocrisy in general, and even less on this "gotcha" kind. Truth is that immigration policy is terribly important to determining what kind of nation you're going to have; if it increases or decreases the deficit a bit, that's really no reason to support or oppose the policy. And $200B or so over ten years is really nothing to get all excited about. It's more the other way around: anyone who claims to care about deficits would have some obligation to change the bill if the estimates had come back the other way; finding that there's a bit of deficit reduction certainly doesn't oblige people otherwise concerned about deficits to support the bill.
Ah, but there's one group which really should weigh in: the professional deficit scolds. Alan Simpson and Erskine Bowles, for example. That is, they should weigh in if they really want people to take them seriously.
First of all, they (and anyone else whose primary political project is deficit reduction) should be out there backing up the CBO estimates. It's not their job to say that anyone who cares about deficit reduction should vote for the immigration bill, but it is their job -- if they really care about deficit reduction -- to do whatever they can to establish the idea that CBO projections are real, and should be treated as real.
(That's assuming, of course, that they agree with CBO; if not, it's their obligation to do a serious nonpartisan critique).
Second, they should be quick to praise those who propose major legislation that helps the deficit. Not the bill itself; again, even deficit scolds shouldn't be suggesting that people support or oppose major substantive legislation because of relatively minor deficit reduction. But there's little reward out there for what deficit scolds certainly should be thinking of as acting responsibly -- the difference, in other words, between Bush-era Medicare expansion and Obama-era ACA. Indeed, that could be especially helpful for deficit-scolds who oppose a bill: "I'm against this, but the authors deserve considerable credit for doing it in a fiscally responsible way."
In fact, however, most deficit scolds typically do no such thing. Which is why no one should take most of them seriously on deficits. And why many who otherwise would be sympathetic to their supposed cause wind up thinking that their real goals have little to do with deficits and debt.