President Trump will cast the Republican tax reform effort as a boon to the middle class Wednesday in a speech in Springfield, Mo., that his advisers say won't include major details.

Instead, the address to be delivered at the Loren Cook Co., a ventilation product manufacturer, is going to be "a 'why,' not 'how,' speech," according to a senior White House official who briefed reporters.

The details of tax legislation will be left up to Republicans on Congress' tax-writing committees. Lawmakers such as House Speaker Paul Ryan and Ways and Means Committee Chairman Kevin Brady have traveled across the country over the congressional recess to tout the tax reform push.

Trump chose Springfield for the first tax reform tour stop because it is an example of a once-great American commerce hub where the middle class no longer prospers as it once did, according to the official.

The speech will focus on "this feeling that the economy is rigged, that it only benefits a small wealthy and well-connected few. And the president is really going to hammer on that," the adviser said.

Past versions of Trump's tax plans would have entailed major tax cuts for high-earning individuals, not the middle class, according to outside analyses.

The Trump officials who spoke to reporters Tuesday, however, suggested that Trump would be successful in framing the tax package as helpful to workers by highlighting how it would make U.S. companies more competitive and by wrapping it in Trump's broader "America First" rhetoric.

One official warned reporters not to "underestimate the economic understanding of the American worker out there, middle-class, blue-collar folks in Michigan, in Ohio, in Pennsylvania, in other states around the country, who have watched the tax code, the tax system as it is today, play a huge role in their factories closing and being shipped overseas."

Treasury Secretary Steven Mnuchin in recent weeks has noted that the corporate tax is shouldered largely by American workers, claiming that workers would see the vast majority of the benefits of a reduction in the corporate rate from the current 35 percent. Mnuchin has said that four-fifths of the corporate income tax is borne by workers, while official estimates from the Treasury Department suggest that business owners pay the majority of corporate taxes. Democrats generally portray corporate tax cuts as benefiting investors rather than workers.

Nevertheless, an official said Wednesday's address would be "a very bipartisan speech."

It will take place in the home state of Democratic Sen. Claire McCaskill, one of the senators thought to be most vulnerable to a GOP challenger in 2018.

Of all Democrats, McCaskill has sounded the most open to working with Trump on tax legislation, saying in a statement Friday that "this is an area on which I'm optimistic President Trump and I will find common ground."