Such doubts are reflected in a new nationwide Reuters/Ipsos public opinion poll that shows a plurality believe the legislation is a windfall for the wealthy and big businesses.

Some 36 percent of respondents said the rich would benefit most, while another 22 percent said it would be U.S. corporations. Just 13 percent said they believed that the middle class would be the main beneficiaries.

The poll also suggests that the tax plan alone may not fuel Republican turnout in November. Some 55 percent of respondents said the tax plan “makes me more interested in voting for Democrats” or “will not change my interest in voting.”

In interviews with 30 voters in Pennsylvania's 18th district, Reuters found most were ambivalent about the tax cuts. Most acknowledged they would keep more of what they earned. But that did not necessarily translate into support for the legislation or for Saccone, the Republican congressional candidate.

Trump voters Marran and Smith said they were still undecided about next month's contest. In Upper St. Clair, a wealthy Pittsburgh suburb, Republican Bill Hartman, 59, said he plans to cast a vote for Lamb. This despite the fact that Hartman's top tax bracket will drop to 25 percent from 28 percent.

“The tax cut was meant to show (the GOP) did something," said Hartman, who earns more than $100,000 a year selling advertising. "But it was just to help the wealthy.”

In contrast, Glen Laufer, a food service worker in nearby Bethel Park, says he is thrilled about the extra $120 he saw in his paycheck last month. He said he is voting for Saccone. "This gives the middle class more money, which will make people more willing to spend money," Laufer said.

Tax cuts should play well with voters here, most of whom will benefit. The predominantly white district stretches from wealthy southern Pittsburgh suburbs in Allegheny County, down through the middle class community of Washington and into the coal mining and farming territory of Greene County bordering West Virginia.

Pennsylvania's 18th district is wealthier than the national average with median household income of $64,000 in 2016. An analysis by the left-leaning Tax Policy Center has concluded that the top fifth of U.S. earners will get a 2.2 percentage point tax cut from the legislation, compared to a 0.4 percentage point reduction among the poorest fifth.

In a telephone interview, Saccone, the Republican candidate, said small business owners and voters he has met are pleased with the extra income.