I've just learned from a reader that Sen. Gordon Smith (R-OR) has declared that he will very likely vote against cloture on the Lars Larson show today; said that he's dissatisfied with present amendment scheme. He's proposing his own variant of an immigration bill. Link the Larson recording here.
Smith said he's trying to "stay constructive," so he won't say for sure, but this is pretty strong against cloture. Says that "at this point" he'll "vote the way he has before," so it seems that, for now, he's pretty anti-cloture. Calls the Z-visa proposal "amnesty." I'd place him somewhere between "Somewhat Unlikely to Switch" and "Very Unlikely to Switch."