Senate Majority Leader McConnell

The Senate was expected to pass a reconciled tax overhaul bill late Tuesday night, with the House re-voting on the same measure Wednesday to send the bill to President Donald Trump for his signature. The new law would be the first major tax reform in 30 years.

The House initially passed a reconciled measure early Tuesday but it included three portions that would violate Senate budget rules. Thus, the Senate was to strip them out before voting Tuesday night and sending it back to the House for full approval.

But Republicans, who promoted the measure without a single Democratic lawmaker’s backing, could face more party-line bickering. Included could be end-of-year battles that might lead to a government shutdown, save part of the Affordable Care Act, threaten the long-term integrity of Medicare or a combination of the above.

Some 189 House Democrats threatened in a letter to House Speaker Paul Ryan (R-WI) to allow automatic spending cuts triggered by the new tax bill to take effect next year unless Ryan ends an attempt to cripple Obamacare.

The 2010 PAYGO law would force a $1.5 trillion government spending cut as revenues fall due to the tax changes. PAYGO mandates years of across-the-board cuts to programs including Medicare starting next year, according to Bloomberg.

Both Ryan and Senate Majority Leader Mitch McConnell (R-KY) have said they will not allow the cuts, but they’ll need help from Democrats to uphold that pledge.

In exchange for supporting a waiver, Democrats want to keep the Affordable Care Act mandate that requires individuals to buy health insurance, which was eliminated by the tax bill.

“Should you enact a tax bill by the end of the year that adds $1.5 trillion to the deficit and, as a result, triggers PAYGO cuts next month, any effort to mitigate those cuts must also remove these other catalysts of uncertainty,” the Democrats wrote to Ryan. “At a minimum, that must include rejecting the elimination of the individual mandate as well as the use of reconciliation procedures next year for Medicare benefit cuts in order to fill the fiscal gap left by your tax bill.”

Some conservative Republicans may favor across-the-board spending cuts and vote against a PAYGO waiver.

Others have already said they’d vote against a bill that includes the cost-sharing reduction payments Democrats want without explicitly prohibiting those dollars from being used for abortion services.

Bloomberg reported Ryan and McConnell could add a PAYGO waiver to a stop-gap bill preventing a government shutdown, which must also pass by Friday to keep federal offices open.