Just under one in five respondents expect to see either a raise or a bonus thanks to the law’s business tax cuts. Early returns from public companies indicate that’s an overshot. Just Capital, a nonprofit research organization, analyzed the 90 largest public companies that have announced how they will spend the combined $45 billion in savings they stand to receive from the tax bill this year. It found that those companies planned to pass 6 percent of those savings directly on to workers, with more than half of that spending in one-time bonuses.

“That does not really track to how the public thinks the companies should be spending that money,” said Martin Whittaker, Just Capital’s chief executive.

Only one in three respondents expects to receive a tax cut from the law. The independent Tax Policy Center in Washington estimates that four in five Americans will actually see a tax cut from the law this year, though that number is projected to shrink sharply in 2027 if individual tax cuts expire as scheduled in the law.

Republicans are confident that support will continue to grow as more Americans see lower taxes reflected in their paychecks. Their confidence was reflected last week by Representative Kevin Cramer of North Dakota, who cited Senator Heidi Heitkamp’s vote against the tax bill when announcing he would run for her seat.

“There is no question the tax bill has fundamentally improved the overall political environment for Republicans,” said Josh Holmes, a former campaign manager and chief of staff for Senator Mitch McConnell of Kentucky, the majority leader, who is now president of the public affairs firm Cavalry in Washington.

Close to half of Americans now expect some direct benefit from the law — either a tax cut or a salary increase or bonus. Support for the bill is far stronger among that group: More than three-quarters of Americans approve of the law, compared with fewer than a third who don’t expect a benefit or aren’t sure.

Gina Coats, a project manager for a plumbing company in Springfield, Mo., said she didn’t follow the tax debate closely last fall. But in January, when she began preparing the company’s payroll systems to handle the new law’s provisions, she realized almost every employee would take home an extra $20 to $40 per week.