President Trump’s economic advisers are exploring whether the president should campaign for reelection proposing a 15 percent tax rate for the American middle class, with some seeing the idea as a simple way of selling Republicans’ economic agenda as not merely beneficial to the rich, according to multiple people involved in the White House’s internal deliberations over “tax cut 2.0.”

Larry Kudlow, director of the White House National Economic Council, is spearheading the effort behind Trump’s second tax cut package and is widely seen as a leading proponent of the new 15 percent rate. It is unclear if Trump has approved the idea, but the president has pushed aides to develop a simple tax message for 2020 focused on middle class tax relief.

The White House has faced sharp criticism for its 2017 tax law, because its tax cuts for individuals and families will expire in a few years but the reductions for businesses are permanent. The new plan is unlikely to pass Congress before the 2020 election but would give the White House a specific plan to present to voters during next year’s presidential campaign.

Reducing the tax rate to 15 percent for middle-class taxpayers would lower taxes by hundreds of billions of dollars, according to budget experts, although precise estimates are impossible given that details remain vague. Doing so would free up much more money for Americans to spend, but it would also dramatically add to the deficit unless the cuts were offset by major spending reductions to federal programs. The GOP tax law of 2017 already added more than $1.5 trillion to the national debt.

Kudlow declined to comment on what the administration was considering, but stressed in an interview that the process is still in its preliminary stages and that no final decisions have been made.

“[Trump] wants to afford as much relief and simplicity as possible for middle-income taxpayers,” he said.

Other ideas that have been discussed include a payroll tax cut, revamping how capital gains are taxed, exempting savings from taxes, and reducing the number of tax brackets from seven to somewhere around three or four, according to Stephen Moore, a conservative tax expert at the Heritage Foundation who has worked with the White House on tax policy.

One senior administration official, speaking on the condition of anonymity to discuss internal deliberations, downplayed the likelihood the payroll tax would be in the final package, citing its potential impact on financing Social Security.

Democrats and other experts have dismissed talk of a second round of tax cuts as a way for Trump to deflect from controversial parts of the 2017 legislation, which permanently cut taxes for corporations but only temporarily cut taxes for individuals. Speaking in New York on Tuesday, Trump defended the 2017 tax cut, saying it had provided “massive relief” for middle class families.

“We think we can bring it down still more,” Trump said of U.S. tax rates.

The details of the second tax package may not be released for months.

Asked by CNBC on Tuesday if the White House is considering a 15 percent tax rate for the middle class, Kudlow said: “I don’t know, sounds like a pretty good idea to me. But I’ve got to consult with a lot of people, and I’ve got to get the president’s sign-off before anything comes out ... Those conclusions will not come for many months.”

Weeks before the 2018 midterms, Trump suddenly floated a 10 percent tax cut for the middle class, saying he was working on a “very major tax cut for middle-income people.” Talk of that plan fizzled after the election and a concrete proposal never materialized.

“Depending on where it starts, a 15 percent rate would be a relatively small tax cut for middle income people,” said Michael Linden, a tax expert at the Roosevelt Institute, a left-leaning think-tank. “This is an acknowledgement that Republicans’ original tax plan was heavily skewed to the wealthy, the middle got almost nothing, and people at the bottom got literally nothing. I’m not sure having a second go at it is going to solve anything.”

Trump initially called for the first Republican tax law to be called the “Cut, Cut, Cut Act," arguing that nobody understands what the phrase “tax reform” means.

Currently, there are seven tax brackets that increase up the income ladder -- 10 percent; 12 percent; 22 percent; 24 percent; 32 percent; 35 percent; and 37 percent. The Republican tax law of 2017 did not reduce the number of federal income tax brackets, but doing so would likely be a part of the “tax cut 2.0” package. The existing 22 percent rate kicks in for single Americans earning more than about $39,000, while the 32 percent rate applies to single Americans earning more than $160,000.

While details remain in flux, Moore said one possible plan would retain the existing tax rates at 10 percent and 12 percent for the bottom two tax rates, as well as the existing top three tax rates. The plan would likely aim to bring down to 15 percent the rates for those who earn between $30,000 and $100,000, Moore said. (The current marginal tax rate for someone making $90,000 is 24 percent.) Doing so would give tax relief to the middle class and the rich, since the rich also pay marginal taxes on the lower rates.

Former Florida governor Jeb Bush (R), during his 2016 presidential run, put out a plan to create three tax rates of 10 percent, 25 percent, and 28 percent that would have cost more than $3 trillion over 10 years, according to Marc Goldwein, a budget expert at the Committee for a Responsible Federal Budget.

“We don’t have enough detail to estimate the impact of this proposal," but it could cost more than $1 trillion depending on how it is structured, Goldwein said.

It is unclear if Republican lawmakers in Congress will embrace a 15 percent tax rate. Republicans only made the corporate tax cut permanent under their law, while parts of the legislation on the individual side of the tax distribution are set to expire, including an expansion in the Child Tax Credit.

At a recent meeting of the National Taxpayers Union first reported by Politico, Kudlow repeatedly extolled President Ronald Reagan’s 1986 tax legislation for creating only two federal tax rates, at 15 percent and 28 percent, according to two people in the room for the speech. Kudlow served in the Reagan administration at the time the 1986 law was written.

“He mentioned that again and again and again,” said one Republican tax consultant who was in the room for Kudlow’s talk and spoke on the condition of anonymity to discuss off-record remarks.

Moore, the Heritage economist, said he is also pushing for a change that would allow capital gains to “roll-over” tax-free if they are reinvested in a different stock. Under this plan, an investor could sell stock in General Electric and reinvest it in Uber without paying a tax on the realized stock gains, as the investor would under current law.

Another idea being floated by outside advisers is to allow savings to be deducted from individuals’ income tax, as a means of encouraging more savings by American consumers, Moore said.

David Lynch contributed reporting to this story.