Nearly three-quarters of Americans believe that the tax system favors the wealthy — and half of Americans believe that President Trump's tax plan will help the rich even more, according to a new Washington Post-ABC News poll.

More than 7 in 10 adults say the nation's tax system already tends to favor the wealthy more than the middle class, with a 55 percent majority who feel this “strongly.”

About half expect Trump's tax plan will disproportionately benefit wealthy Americans, 51 percent, while 10 percent think it will mainly benefit the middle class, and 24 percent say it will benefit both groups equally.

Republicans are expected to outline their tax plan this week, fueling intense speculation about how much taxes will be cut and whether the benefits will accrue mostly to rich people or also to the middle class.

When asked if they support Trump’s tax plan, opposition outpaces support by 44 to 28 percent, with nearly 3 in 10 saying they have no opinion.

A majority of Americans also believe that large corporations pay too little in taxes. But they are split on whether taxes on businesses should be reduced.

Republicans are aiming for a corporate rate of 20 percent in their tax overhaul plan, a large cut from the current 35 percent rate but still short of Trump's goal of 15 percent.

But the Post-ABC poll finds 65 percent of Americans say large corporations pay too little in taxes while 11 percent say they pay too much; 17 percent say they pay about the right amount.

Over three-quarters of Democrats and about 7 in 10 independents say corporations pay too little in taxes. Among Republicans, 47 percent say big corporations pay too little while 17 percent say they pay too much. Another 27 percent of Republicans say corporations pay their fair share of taxes.

Despite perceptions that large corporations pay too little, a sizable 45 percent support lowering taxes for business in general, while 48 percent oppose such a change. That difference is within the sampling margin of error of the poll, which is plus or minus 3.5 percentage points. Most Republicans support lowering taxes on businesses, while most Democrats and half of independents are opposed.

Far more popular is reducing taxes on middle- and lower-income people — 78 percent support such a move, including overwhelming majorities across party lines — while less than half as many support lowering taxes on those with higher incomes. Most Republicans support lowering taxes on businesses, while most Democrats and half of independents are opposed.

Eric Toder, a co-director of the Urban-Brookings Tax Policy Center, said that from what little is known about Trump's tax plan, the public is right that it will favor the wealthy. “If that's what they believe, they figured something out,” Toder said.

But contrary to public perception, Toder said the current tax code does not actually favor the wealthy over poor people. Generally, wealthier people pay higher taxes, and many low-income people pay no taxes at all.

An exception is at the highest end of the income spectrum, where some wealthy individuals pay a lower rate by taking advantage of deductions, credits and other tax preferences built into the system.

An important question for policymakers to examine, Toder said, is why people with the same income will sometimes pay very different tax rates.

Toder said that since the 1980s, corporate taxes have overall comprised about 2 percent of growth domestic product. He argued that many people in the public fail to appreciate that the taxes on corporations are actually taxes on the individuals who own the corporations — which includes corporate officers and high-income people, but also regular investors, pension plans and people who invest through their retirement accounts.

The perception that corporations short the tax man is a half-century old. When a 1977 Roper poll also asked Americans whether large business corporations paid the right amount of taxes, 73 percent said they pay too little, eight points higher than the current poll.

The Post-ABC poll was conducted Sept. 18 to 21 among a random national sample of 1,002 adults reached on cellular and landline phones. Overall results carry a plus or minus 3.5-point margin of sampling error.

Scott Clement contributed to this report.