The GOP-led Congress’s sweeping tax reform plan appears to have enough support for Senate passage -- with the apparent backing of several Republican senators whose nonsupport for the effort to repeal and replace Obamacare doomed the effort this summer.

House and Senate negotiators agreed Friday on a compromise bill that offers a substantial tax cut for corporations and across-the-board cuts for individuals, with final votes in the respective chambers expected next week.

Among those supporting the bill -- a blend of the House and Senate versions -- is Sen. Susan Collins.

The Maine Republican said this summer, with state residents in mind, that she opposed the Obamacare overhaul measure because Medicaid cuts were too deep, and because it didn’t go far enough to protect people with pre-existing conditions like diabetes or cancer.

However, the four-term senator told The Washington Post that she is supporting the tax overhaul, the largest in roughly three decades, in exchange for promises from the Trump administration and Senate leaders to put more money into the country’s health care system.

“This bill is far from perfect. But after great thought and consideration, I believe that this once-in-a-generation opportunity to make U.S. businesses domestically more productive and internationally more competitive is one we should not miss.”

— Sen. Bob Corker, R-Tenn.

The final version is expect to pass the House despite some immediate opposition.

“The bill agreed to in conference today makes some improvements,” said Rep. Darrell Issa, R-Calif. “Unfortunately, the changes do not go far enough to guarantee tax relief for constituents in my district. … I will not vote to make the incredible tax burden they already endure even worse.”

However, Republicans’ 239-193 House majority over House Democrats should be sufficient to overcome any party opposition.

The change will take effect in 2018 if Trump signs the bill by Dec. 31. However, taxpayers won’t see the impact until spring 2019 when they file their 2018 returns.

"I’m excited to announce if Congress sends me a bill before Christmas, the IRS -- this is just out, this is breaking news -- has just confirmed that Americans will see lower taxes beginning in February,” Trump said Wednesday. “Just two short months from now.”

Passage in the Senate became more of a challenge last week, when Democrats won the Alabama Senate seat left open after Republican Sen. Jeff Sessions became U.S. attorney general. The victory cut the GOP Senate majority to 51-49. (No congressional Democrat has voted for any version of the tax reform plan.)

The Senate bill, which was melded with the House version, passed in the upper chamber in early December with relative ease, with Sen. Majority Leader Mitch McConnell, R-Ky., keenly aware of his support and determined to avoid another setback like the failed Obamacare vote.

The measure passed 51-49, without Vice President Pence needing to cast a final decisive “yes” vote.

Tennessee Sen. Bob Corker, who has frequently clashed with President Trump, was the only Senate Republican to vote in opposition. However, he now appears ready to support the tax plan and give the president his first major legislative win.

“This bill is far from perfect," Corker said. "But after great thought and consideration, I believe that this once-in-a-generation opportunity to make U.S. businesses domestically more productive and internationally more competitive is one we should not miss.”

The $1.46 trillion tax overhaul plan almost crumbled this week amid opposition from Sen. Marco Rubio. But the Florida Republican relented after the negotiators expanded the tax credit that parents can claim for their children.

Collins,  Lisa Murkowski of Alaska and John McCain of Arizona were the three GOP senators who effectively scuttled the chamber’s Obamacare repeal-replace effort, with McCain casting the decisive no vote.

McCain and fellow Republican Sen. Thad Cochran of Mississippi voted earlier this month in favor of the Senate tax bill but missed votes this week for health reasons.

The 81-year McCain is in a Washington-area military hospital being treated for the side effects of brain cancer treatment. And the 80-year-old Cochran had a non-melanoma lesion removed from his nose earlier this week.

GOP leaders are hopeful they will be available next week.

The Associated Press contributed to this support.