President Donald Trump's is set to make a major tax reform speech on Wednesday, and the content of the speech was shaped by top nationalist White House aide Stephen Miller, Politico reports.

The development could come as a surprise to markets, as Trump cabinet members Steven Mnuchin and Gary Cohn, both former Goldman Sachs executives, had been leading the effort to craft tax reform policy.

Yet, the New York Times reported Monday that some conservatives were concerned about the involvement of the two ex-bankers.

Politico reports that in his speech, Trump is likely to pledge to eliminate deductions that overwhelmingly benefit higher-income tax payers.

While Politico said that the president's speech is unlikely to go into specifics about which deductions will be targeted, it's expected he will characterize his plan as one that levels the playing field for his populist base.

The prospect of tax reform was a major catalyst for the stock market after Trump's win in November. Reports of lawmakers finding common ground on the issue have buoyed trader optimism, while any potential catalysts for delays have sent jitters through the market.

Read the full report on Politico.