Paul Ryan just undercut a major Republican argument about the GOP tax bill

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• Paul Ryan said Wednesday that "nobody knows" if the tax bill will pay for itself, after GOP leaders argued for months that it would.
• Most major analyses show that the bill would not pay for itself.

 
At the outset of the Republican push to overhaul the US tax code, GOP leaders said reform would boost economic growth, help the middle class, and - importantly for the fiscal future of the US - pay for itself.

Now, as Congress is on the edge of finally passing the massive tax bill, House Speaker Paul Ryan suggested he's not so sure about the final piece of those promises. Ryan was asked on NBC's "Today" show whether or not the tax bill will increase the deficit or if it will pay for itself.

"Nobody knows the answer to that question, because that's in the future, but what we do know is that this will increase economic growth" Ryan said.

The GOP is in agreement that the "static" impact of the tax bill - the addition to the debt with no economic growth assumptions - will be just under $1.5 trillion in new debt. The question is whether the economic growth that the Tax Cuts and Jobs Act (TCJA) produces can generate enough new tax revenue to make up that gap.

While Republican leaders argued it would, every major independent analysis of the TCJA showed the bill would grow the federal debt over the next 10 years even when accounting for that increased growth.

Major analyses predicted that the bill will be a modest boost for the US economy, increasing the US GDP growth rate anywhere from 0.08 percentage points a year to around 0.35 points a year. But, none of the models show the growth will be enough to pay for the bill.

The right-leaning Tax Foundation, which is aggressive in its growth assumptions, estimated that the final bill will add $448 billion to the deficit over the next decade. The Tax Policy Center estimated that debt increase would be closer to $1.2 trillion. The official congressional scorekeeper, the Joint Committee on Taxation, said that even with the growth the TCJA would add $1 trillion in new debt.

A much maligned report from the Treasury Department said that the tax bill would need to be coupled with other economic policies to make up for the new debt.

Ryan eventually pivoted to another way to make up for the new debt the bill would add: spending cuts.

Watch Ryan's response here: