Brian Faler, the news outlet's senior tax reporter, emphasizes, "There’s a chicken-and-egg quality to the debate though, because it’s hard to know how much they need to raise when they haven’t decided how much to spend. And lawmakers will be subject to furious lobbying by those worried they’re on the menu."

Faler reports, "Deficit concerns are running hot in the House, where many Republicans say a tax bill ought to be completely paid for," but, "That’s anathema to party heavyweights like House Ways and Means Chair Jason Smith (R-Mo.) and Senate Finance Chair Mike Crapo (R-Idaho), not least because it would be extremely difficult to find enough offsets to cover the projected $4 trillion cost."

Faler also notes:

Smith has already signaled he’s ready to deal on the $10,000 cap on state and local tax deductions, amid pressure from colleagues representing high-tax states. Sen. Josh Hawley (R-Mo.) recently proposed a big, pricey increase in the child credit, to a maximum $5,000, from the current $2,000, per kid. Rep. Darin LaHood (R-Ill.), meanwhile, just rolled out a plan seconding Trump’s bid to cut income taxes on Americans living abroad.

There will only be more as the debate heats up, and a key challenge for party leaders will be figuring out how to contain what could be mushrooming demands from their colleagues that would wreck their budget numbers.

Furthermore, the Politico reporter adds, "They’ll have to raise the debt limit too, after a last-minute bid by Trump to increase it before he comes into office, was rejected. And Republicans are promising to also cut mandatory spending by $2.5 trillion. If any of those things get bogged down, that could push off the tax debate even further."