Preparing for a showdown over revenue, Democrats are mobilizing groups such as Nuns on the Bus, a Catholic advocacy group that organized a tour in 2012 to protest Ryan’s budget blueprint on moral and religious grounds because of its cuts to programs like food stamps that feed the poor and children.

‘Reasonable Revenue’

“We are urging reasonable revenue,” said Sister Simone Campbell while visiting the Capitol on Nov. 5. “It is wrong to just think you can cut.”

Republicans say they already voted for a tax increase, citing a law passed in January that let the top income tax rate rise to 39.6 percent. They also say the revenue collected from ending tax preferences is needed to help pay for lowering income tax rates for everyone as part of a broader tax overhaul.

“They’re pushing every little approach they can” to raise taxes, said Orrin Hatch, a Utah Republican and the top Republican on the tax-writing Senate Finance Committee.

“They would like to snooker Republicans into just doing one part of tax reform. We can’t do that because you’re going to need all parts to come up with something that works.”

$1 Trillion

With an estimated $1 trillion in such revenue at stake, Murray and other Democrats say it isn’t a credible position. “I don’t buy it,” she said.

There is some truth to both arguments, said Roberton Williams, a tax fellow at the Tax Policy Center in Washington. “It’s a matter of degree rather than black and white,” said Williams, a former Congressional Budget Office staff expert.

“If you get rid of some of the loopholes there will be less available to buy down tax rates. But will there still be a lot left? Yes,” he said. “But you’re taking away some of the easiest ones they can agree on.”