Donald Trump secured his first major legislative victory as president Friday, signing a sweeping Republican tax measure into law as he closed out a turbulent 2017 at the White House.

After a raucous celebration with Republican lawmakers Wednesday on the White House’s South Portico — during which senior GOP members lavished him with effusive praise — Trump opted to sign the bill in the Oval Office rather than hold another signing ceremony.

The measure lowers the corporate rate to 21 percent and cuts taxes across the board, both longtime goals for Republicans. For Trump, putting his signature on the legislation fulfills what was one of his biggest campaign promises.

In recent weeks, Trump has called the tax measure a “big, beautiful Christmas present” for the American people and U.S. businesses. Senior White House aides say the president himself came up with that “branding” for the measure.

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But it represents a triple win for Trump and Republicans. That’s because the bill, which passed both the House and Senate without a single Democratic vote in support, also zeroed out the penalty for not buying health insurance as part of the 2010 health care law and opened the Arctic National Wildlife Refuge to energy drilling.

Trump and GOP lawmakers are hopeful the tax cuts will help them in the 2018 midterm elections — and the House and Senate likely will be in play next November.

“This is a huge win for the president, congressional Republicans and their allies, but — more than that — it is a victory for cash-strapped middle class families,” Michael Steel, a GOP strategist who worked for Jeb Bush’s 2016 campaign and former Speaker John A. Boehner, said this week.

“By lowering tax rates, expanding the standard deduction, and expanding the child tax credit, this law will put more money in people’s paychecks,” Steel said. “By cutting the highest corporate tax rate in the developed world, it will create more jobs and increase wages. And, by repealing the unpopular individual mandate in Obamacare, it fulfills a long-held promise to voters.”

Key GOP lawmakers heaped praise on Trump as they celebrated their first mutual victory on Wednesday as members lined up on the South Portico’s tall staircases, snapping selfies and letting out a loud cheer when Trump joined them.

“You’re living up to everything I thought you would,” Senate Finance Chairman Orrin G. Hatch of Utah told him on a chilly December afternoon. “You’re one heck of a leader.”

“Look at all the things that he’s been able to get done, by sheer will in many ways,” Hatch added, urging his GOP colleagues to “get behind [Trump] every way we can.”

In a striking comment, Hatch — whom the president is urging to seek another term after he turns 84 in March — said Trump’s presidency could eventually become “the greatest presidency we have seen not only in generations but maybe ever.”

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Democratic members, however, have the opposite view of the tax bill.

“This tax bill will be an anchor around the ankles of every Republican,” Senate Minority Leader Charles E. Schumer said this week.

He and other Democrats — backed by independent economists — warn the GOP tax measure will balloon the federal deficit and help the wealthiest earners and large corporations while failing to live up to Trump’s promises about the middle class.

“Yesterday in the Oval Office, President Trump admitted that cutting the corporate tax rate was ‘probably the biggest factor in our plan,’” Schumer said Thursday. “Despite all his rhetoric about this being a middle-class tax bill, as soon as it passes, he admits that lowering the corporate rate was the Republicans’ primary goal.”

“As corporations get a massive, permanent tax break,” he said, “individuals will get small and temporary ones.”

And Senate Appropriations member Jack Reed of Rhode Island is warning that the deficit effects of Trump’s first major legislative win will make things like his long-promised infrastructure overhaul and military buildup unaffordable.

“I don’t see where they have the resources,” he told Roll Call on Thursday.