The Senate Budget Committee has voted to advance the Senate tax bill by a 12-11 margins, with only Republicans voting in favor, CNBC reports.

“Republican Senate leaders want to pass the plan later this week. As it holds 52 seats, the GOP can lose only two votes and still approve the bill under special budget rules, assuming all Democrats and independents oppose it.”

The Wall Street Journal identifies three blocs of Republican senators who have not yet committed to supporting their party’s tax bill.

“One group, including Ron Johnson (R-WI) and Steve Daines (R-MT), wants deeper tax cuts for so-called pass-through businesses such as partnerships and S corporations that pay taxes on individual rather than corporate tax returns…. Another group, including Bob Corker (R-TN), Jeff Flake (R-AZ) and James Lankford (R-OK), is concerned about the $1.4 trillion addition to budget deficits the bill would cause… A third group, including Susan Collins (R-ME) and John McCain (R-AZ), helped kill the Republican health-care bill earlier this year and could pose resistance over a variety of provisions, including plans to repeal the Affordable Care Act’s health-insurance mandate as part of the tax bill.”

Axios: What Lankford, Flake and Corker want before voting on tax bill.

Ezra Klein: “Over the past week, I’ve been speaking with conservative tax experts to try to better understand their case for the Senate’s tax bill, which Majority Leader Mitch McConnell is rushing to pass this week. What I’ve found is jarring.”

“Plenty of right-leaning wonks will make the case for cutting corporate taxes and reforming how they’re collected. But it’s harder to find those who think the way this bill goes about it, or finances it, makes much sense.”

“What’s worse: There’s wide agreement that pretty much everything else in the bill — and there’s a lot of other stuff in the bill — is done badly, in ways that are going to create unnecessary problems down the road.”

Mike Allen: “With administration and leadership aides frantically negotiating with holdout senators, the Senate’s tax vote scheduled for late this week could lapse into next week.”

“That would raise everyone’s blood pressure: Everything is fragile.”

“The bill is in the ugly sausage-making phase, with senators taking advantage of their leverage to make demands. At least six GOP senators are holding out (John McCain and Jeff Flake of Arizona, Bob Corker of Tennessee, Susan Collins of Maine, Ron Johnson of Wisconsin and Steve Daines of Montana). Lose three of those, and the bill is dead.”