President Donald Trump said his tax plan would simplify the tax code and save money for millions of U.S. businesses and families as he campaigns against criticism the proposal is a giveaway to the rich.

“All I can say is, ‘you better get it passed,’’’ Trump said of Congress on Wednesday in Harrisburg, Pennsylvania, during a speech to a group of truck drivers. “They will, I know.”

Democrats say that the tax overhaul’s benefits are skewed to the wealthy, and an independent analysis found that the plan may actually raise taxes on nearly a third of middle-class families, criticism that is weighing on Trump’s plan. A study by the nonpartisan Urban-Brookings Tax Policy Center, which used details from previous Republican plans to fill in gaps in the president’s framework, found the Trump plan would raise taxes for almost 30 percent of filers making $50,000 to $150,000 per year.

The president pushed back in Harrisburg, arguing that the tax cuts for corporations that are a centerpiece of his plan ultimately would help middle-class families. Trump said as corporations get to keep more of their profits, they will use some of the added income to pay workers higher wages. That shift along with bringing offshore earnings back to the U.S. would translate into a $4,000 pay raise for an ordinary worker, Trump said.

“We can breathe new life into struggling industries and forgotten towns,” Trump said.

Economists disagree on just how much individuals benefit from corporate tax breaks, but even Trump’s own economic advisers have said that the $4,000 benefit would only materialize over eight years. On an annual basis, it’s closer to $500.

Trump has repeatedly pitched the tax plan that he and congressional leaders released last month as a boon for middle-class families. But until now, he hasn’t offered many specific numbers to back that claim -- and the plan itself contains too few details to determine its precise effects across individual income levels. In citing the $4,000 figure, the White House chose the low end of a range of estimates provided by Trump’s Council of Economic Advisers, a senior White House official said.

Trump’s visit to Harrisburg continued his effort to drum up support for his tax proposal by putting pressure on vulnerable Democrats in the Senate.

Pennsylvania Senator Bob Casey is up for re-election in 2018, one of 10 Democrats running in states won by Trump. Trump has previously traveled to Indiana, North Dakota and Missouri to give speeches on the tax proposal, singling out Democrats who face tough re-election bids next year.

“Congressional Republicans are not pursuing tax reform, just a massive tax giveaway to the super-rich at the expense of the middle class,” Casey said in a statement issued almost as soon as Trump stopped speaking. “Eighty percent of the Republican tax plan goes to the top 1 percent by 2027 -- that’s a bad deal for middle class families and workers.”

Trump’s tax proposal also faces some resistance from Republicans, including Senator Bob Corker of Tennessee. Trump has engaged in a public battle with Corker, attacking the two-term Senator over his height and his decision not to pursue re-election.

On Tuesday, Trump said he did not believe his feud with Corker would impact the tax debate.

“People want to see tax cuts, they want to see major reductions in their taxes, and they want to see tax reform -- and that’s what we’re doing,’’ Trump told reporters at the White House. “And we’ll be adjusting a little bit over the next few weeks to make it even stronger.‘’

The president may try to reinforce his message during an interview with Fox News Channel host Sean Hannity that was also part of his Harrisburg schedule.