After more than 100 days of President Trump marked by overreach and economic self-immolation, congressional Republicans need a reset to save their political fortunes. Representative Mike Johnson, the House speaker, is banking on a spending and tax cut package to provide that jolt, and numerous House committees are now working quickly to stitch together a bill he has pledged to deliver to Mr. Trump before Independence Day.

This “one big, beautiful bill,” as Mr. Trump has called it, contains most of the president’s legislative agenda. Indeed, the strategy is making the bill too big to fail, betting that wavering members will not be willing to vote against it and deliver the leader of their own party such a stinging defeat.

But what if it does pass and voters barely take notice?

The details are still being worked out, but the bill could include cuts to Medicaid, as well as funding increases for immigration enforcement and the military. But the heart of the bill is extending the 2017 tax law, primarily the reduced personal income tax rates. With the economy teetering from the president’s foolhardy use of tariffs, the administration has said extending the law is an urgent imperative that will calm markets and provide an economic boost.

The Republican congressional leaders, Senator John Thune and Mr. Johnson, should not talk themselves into believing that this bill will deliver Republicans from the effects of Mr. Trump’s tariffs. The leaders face converging political problems right now: All the party’s energy is directed toward passing this one bill, for which voters may not reward them, and the effort is likely keeping them from putting more pressure on Mr. Trump to stop the tariffs.

Many Republicans are hoping that the tax bill can blunt the economic damage caused by the Trump tariffs, but that is highly unlikely. The way Mr. Trump in particular is talking about the legislative package is doing them no favors. He and Republican leaders have sold the extension of the tax law as tax cuts “for everybody.” It will be “the biggest bill in the history of our country, in terms of tax cuts and regulation cuts and other things,” Mr. Trump said last month. But the reality is it’s no cut at all for most people. The rates they are preserving have been in place for more than seven years now.

In 2017, as counselor to House Speaker Paul Ryan, I helped pass the Tax Cuts and Jobs Act. It was a significant achievement, I remain proud of it and I’ve worked with groups that want to extend it. The law made American businesses more competitive by permanently lowering the corporate tax rate and eliminating scores of unproductive carve outs for businesses. It simplified the individual tax code and brought meaningful relief to families in almost every tax bracket. The scale of its ultimate economic impact was muddied by Covid, but I have no doubt it contributed to the robust economy that preceded the pandemic.