On CNN on Sunday, however, he said that parts of the bill were worth saving.
"According to the Tax Policy Center, next year, 91 percent of middle-income Americans will receive a tax cut," CNN's Jake Tapper asked Sanders. "Isn't that a good thing?"
"Yes, it is a very good thing," Sanders said. "And that's why we should have made the tax breaks for the middle class permanent. But what the Republicans did is made the tax breaks for corporations permanent, the tax breaks for the middle class temporary."
The first part of Sanders' answer went viral over the sleepy holiday weekend. It was, said Republicans, evidence that the tax cut bill - by some measures, the least popular piece of major legislation in this century - would become hard for Democrats to oppose once it was signed. Like the 2001/2003 Bush tax cuts, the temporary nature of the bill's income tax breaks was not just a budget gimmick, but a dare.
"When Bernie comes back to town, he should pledge to vote with Republicans in 10 years to make the tax cuts permanent for the middle class," said Republican National Committee spokesman Michael Ahrens in a Monday statement.
There is little chance of that, but the politics of the tax cut bill are likely to shift in 2018. Both liberal-leaning economists and Democratic politicians expect the tax bill to slightly boost the economy heading into the midterms. Both acknowledge that some voters who expected to face higher tax bills will see benefits. A CBS News video about the tax cuts, which showed three families surprised and happy to learn that they'd be getting money back, circulated widely as a preview of what to expect.
"In order to fit everything into the box, some things need to be temporary," Americans for Tax Reform President Grover Norquist told The Washington Post before the bill passed. "But just as the Bush tax cut was temporary for 10 years, the goal is always to make things permanent. I've always thought that four or five years was fine. Why? Because it will be so politically popular that it's basically permanent. Even the Democrats won't run against the tax cut for individuals. Ask them!"
In some ways, Democrats' tax answers may resemble those they gave when George W. Bush was in the White House. In both the 2004 and 2008 campaigns, the Democrats' presidential nominees proposed benefits for the middle class that would be paid for, in large part, by ending most of the Bush tax cuts.
"To pay for these tax cuts, I'll stand up to special interest carve-outs, close corporate loopholes and offshore tax havens, and ask the wealthiest Americans to give back a portion of the Bush tax cuts," then-Sen. Barack Obama said in a typical 2008 stump speech. "It's time for folks like me who make over $250,000 to pay our fair share to keep the American promise alive for our children and grandchildren."
With relish, Republicans remember how the story ended - with Obama making all but the high-end Bush tax cuts permanent, and neither party absorbing much voter anger for the growing deficit. Since then, the Democratic Party's left wing has grown stronger. Sanders made a strong run for the 2016 presidential nomination on a campaign platform that included tax increases; Sanders has gotten most of the Democratic senators seen as potential 2020 candidates to sign onto a universal Medicare bill, a proposal that would be paid for by tax hikes.
But as Sanders and others have shown in the past week, Democrats are not promising to undo the entire Republican tax bill. While attacking corporate tax cuts, Democrats - including Obama - had been ready to lower the corporate tax rate from 35 percent had Republicans been willing to deal, or had Hillary Clinton won the 2016 election. In a rundown for the progressive Center for Economic and Policy Research, Dean Baker argued that the bill contained some benefits for poorer people, ones that future Congresses should continue.
"There are some items in this bill that can provide a basis for constructive reform in the future," Baker wrote. "These can be built upon at a time when we have a Congress interested in serious reform."
Few Democrats, so far, have been put on the spot about that. One who has, Sen. Joe Manchin, D-W.Va., spent most of a 16-minute interview with radio host Hoppy Kercheval on Dec. 20 defending his vote against the bill. "I was for lowering corporate taxes from 35 to 25," said Manchin, acknowledging what few Democrats will now say. Over the course of the interview, Manchin repeatedly said that there might be a "sugar high" from the bill, and that people might indeed like it.
"Why couldn't you support a bill that will benefit the vast majority of West Virginians?" asked Kercheval.
"The things that you have mentioned are correct," Manchin replied. "Initially, people will benefit."
Manchin's attempts to redirect the questions offered a preview of what other members of his party might say in 2018. Like Sanders, Manchin suggested that Congress "make permanent that anything we did for the working class" - but only as part of a responsible deal that did not blow up the deficit. Manchin also suggested that higher health-care premiums would, for many taxpayers, wipe out any gains from the tax cut, while the idle rich would benefit no matter what.
Later, Manchin found an opening by saying Republicans had failed on a high-profile tax cut promise. "They talked about the postcard, the simplification? Hop, this is more complicated than what we had before," he said.