DENVER (AP) -- Jeb Bush went to Detroit and talked about leveling the playing field. Marco Rubio wrote a book about helping the working class. Rand Paul is promising to expand the Republican Party beyond its traditional base.
Yet all three Republican presidential candidates have offered tax proposals that would, for reasons such as nomination politics and tax rate realities, benefit overwhelmingly the wealthiest.
In doing so, they have drawn criticism from Democrats who call it proof that the GOP's eventual nominee will mainly try to help the rich.
Even some conservatives expressed concerns after Bush released his proposed tax cut this past week. Then there was the analysis Thursday from the Washington-based Tax Foundation that concluded his plan would initially help the top 1 percent of earners 10 times as much as it would those in the bottom 10 percent.
"Republicans should be countering the caricature of themselves as slavishly devoted to the interests of rich people and corporations, not playing into it," according to an editorial in the conservative National Review. The magazine nonetheless praised Bush's effort to reduce income and business tax rates.
The trio's tax plans do contain elements aimed directly at middle- and working-class voters. Rubio proposes to expand the child tax credit and Bush wants to double the Earned Income Tax Credit, which is designed to help the working poor.
But experts note that any broad income tax cut inevitably will benefit the rich more than anyone else, because they pay much more in federal income taxes than the middle class or poor.
About 40 percent of the country does not pay federal income tax. The top 1 percent of earners pays about 35 percent of the income tax.
"It is a mechanical problem," said Howard Gleckman of the Tax Policy Center, a joint project of the centrist Brookings Institute and left-leaning Urban Institute.
"If you start from the place where any tax plan has got to cut tax rates, you start with a plan that is already regressive and it becomes challenging and complicated to ameliorate that."
Michael Strain of the conservative American Enterprise Institute said Republicans have good reason to push for across-the-board cuts, despite the inevitable benefit to the wealthy.
"There's a genuine concern on the part of conservatives about economic growth and having tax code that fosters economic growth because of a belief that you need a growing economy to help everyone in the country," Strain said.
John Cogan, a Stanford economist who served in the Reagan administration and consulted on the Bush plan, argued that the tax reductions can help cure the inequality that critics contend they exacerbate. "Economic growth is absolutely essential to reducing the degree of inequality," Cogan said.
That's how Bush, a former, Florida governor, has tried to sell his plan. On Thursday, he brushed aside Democratic criticisms that the proposal was a giveaway to his wealthy donors and could increase the deficit, under his own supporters' estimates, by more than $3 trillion.
The U.S. must get back to "high, sustained economic growth," Bush said during a CNN interview. "We need to boost people's spirits by giving them more money to be able to make decisions for themselves."
Bush's plan condenses seven different brackets to three — 28 percent for top earners (who are now taxed at as high as a 39.6 percent rate), 25 percent and 10 percent for families making up to $87,000.
He would drop the corporate rate from 35 percent to 20 percent. To help middle- and working-class families, he would double the standard deduction and raise the Earned Income tax Credit.
Bush surprised observers by pledging to eliminate a tax break that benefits investment managers — a small but symbolically potent change to a Wall Street benefit that comes weeks after rival Donald Trump called for such a move.
Florida Sen. Rubio wrote a book in December outlining proposals to help low-income and middle-class families.
In February he signed on to a sweeping tax proposal that does not cut top rates as much as Bush's plan but does eliminate taxes on investment income. That would slash federal tax bills for many of the wealthiest in the country.
Paul, a Kentucky senator, followed with a proposal to drop the tax rate to 14.5 percent across the board, which analysts argue may be an even bigger windfall for the rich.
Conservative commentator Ramesh Ponnuru wrote in a column Thursday that the GOP should look to cutting other levies, like the payroll tax, which fall the heaviest on lower- and middle-income laborers. He said the GOP tax cut plans might end up being compared to Mitt Romney's in 2012, which a majority of voters thought helped the rich, according to exit polls.