WASHINGTON -- Georgia Republicans took a victory lap on Tuesday as their long-awaited tax bill hurtled toward final passage in both chambers of Congress.

The $1.5 trillion legislation constitutes a major political win for the party less than three months after its years-long effort to repeal Obamacare collapsed in the Senate. Lawmakers said the measure's passage marked not only a once-in-a-generation opportunity to make over the tax code, but a key legislative accomplishment Republicans could bring to voters ahead of the 2018 midterms.

"It ain’t bragging to say it’s one of the most unbelievable accomplishments I have seen politically in my 40 years of legislative work," said Republican U.S. Sen. Johnny Isakson. "The obstacles that had to be overcome were many and immense."

In the week since Doug Jones' surprise victory in the Alabama Senate race, Democrats have grown increasingly optimistic about a potential wave at the ballot box next year. Passage of the tax bill, however, arms GOP incumbents with a major political victory on which to hang their hats.

U.S. Rep. Barry Loudermilk, R-Cassville, said the bill's passage "finally gets the momentum changed" on Capitol Hill.

"It shows that we can be unified over conservative principles," he said of congressional Republicans.

GOP confidence comes even as public opinion of their plan remains low. A new NBC News/Wall Street Journal poll found that less than one-quarter of voters thought the measure was a good idea.

Democrats were quick to pounce on those numbers. They framed the Republican tax bill as plan designed to benefit rich donors and argued there would be repercussions at the ballot box next year.

“If I were a Republican, I’d keep the champagne corked," said DuBose Porter, the state's Democratic Party chairman. "What they’ve accomplished is nothing more than another giveaway to the richest in our country at the expense of our middle class."

Unclear is how long the GOP's glow will last. Congress must immediately turn to the prickly task of funding the government, an exercise that will require the cooperation of Democrats. It's likely the GOP will need to make concessions on nondefense spending in order to stave off a weekend shutdown. And the same  issue will almost certainly need to be revisited in January, when Democrats say they'll insist on providing legal status to Dreamers and a larger budget deal.