The Congressional Budget Office said last week that such a repeal would reduce federal deficits by $338 billion over the next 10 years, which would help the GOP avoid exceeding a $1.5 trillion cap on how much the tax bill can add to the deficit over the same time period. The repeal would also increase the number of uninsured by 13 million by 2027, according to the CBO.
Sen. John Thune, R-S.D., a top McConnell deputy, said the savings from the repeal would give Republicans more room to cut taxes for the middle class.
"It will be distributed in the form of middle-income tax relief," Thune said. "It will probably mean adjusting the rate structure as we have today. We'll probably still have seven brackets, but they would be at different rates."
Asked if he was confident such a bill could pass, Thune said yes, adding that leaders had already "whipped" the bill, meaning they already know how their colleagues will vote.
Not all Republicans agree with the decision. Moderate Sen. Susan Collins, R-Maine, said she had not decided how she will vote on the tax bill, but she worries that ending the individual mandate could increase health care premiums.
"I personally think it complicates tax reform to put the repeal of the individual mandate in there," Collins said. "I'm going to wait and see what the bill says."
But adding it in could appeal to other skeptics of the legislation, including Sen. Rand Paul, R-Ky., who supports the individual mandate repeal.
The Senate Finance Committee is expected to release an updated version of the legislation Tuesday evening. The committee plans to approve the bill later this week in hopes of holding a vote in the full Senate before Thanksgiving.
Republicans on the Finance Committee worked around the clock in recent days to try to bring down the long-term cost of their tax bill. Republicans want to take advantage of complicated Senate budget rules, known as reconciliation, that would allow them to pass the tax bill with 51 votes rather than the 60 needed for most other legislation. That would allow the 52 Senate Republicans to pass the bill without the help of any Democrats.
But those same budget rules require that the tax overhaul not add to the deficit after 10 years. The Senate bill appeared to violate those regulations as recently as Tuesday morning. Repealing the individual mandate could help ease the fiscal pressure.
Democrats, enraged over McConnell's announcement, said adding the individual mandate to the legislation effectively ended any chance for bipartisan agreement on taxes. Sen. Ron Wyden, D-Ore., the top Democrat on the Finance Committee, said repealing the mandate would hurt the middle class.
"In their desperation to secure an ideological trophy, no matter the consequences," Wyden said, "Republicans are choosing to pay for corporate tax cuts by raising premiums for middle class families and ripping away health care altogether from millions more.