Donald Trump’s campaign claims his federal tax returns are not of interest to American voters, but that’s actually not true, according to a new Morning Consult poll.

“This is an issue the media is interested in. This isn’t an issue that middle America is interested in,” Trump aide Paul Manafort said on CNN’s “State of the Union” earlier this month.

But a new national survey by Morning Consult of 2,001 registered voters found that 67 percent – and 60 percent of Republicans – think presidential candidates should have to disclose their returns. Just one in five voters (21 percent) said they don’t think the financial documents should have to be released.

Unlike every Republican nominee since Ronald Reagan, Trump has refused to release his tax returns, prompting Democrats – including Democratic front-runner Hillary Clinton – to question what he is “hiding.”

“Trump’s turned refusing to release his taxes into an art form. That’s what you get from a con-man like Donald Trump,” said Justin Barasky, a spokesman for Priorities USA, the main super PAC supporting Clinton’s campaign, in a Monday email launching a new web ad critical of him on the issue.

Many more Republicans, 85 percent in total, said they thought presidential candidates should be required to provide an original copy of their birth certificate, though 67 percent of Democrats and 77 percent of self-identified independents said the same thing.

Almost a quarter (23 percent) of Democrats said they did not think a candidate should be required to release an original birth certificate, an issue perpetuated by Trump, among others, that haunted President Obama through much of his first term.

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Republicans, Democrats and independents expressed similar levels of support when asked if candidates should be required to make public information about their medical history. About half of voters said they should, while 33 percent of voters said they should not.

Clinton released her medical history last July, when a doctor declared her “fit to serve.” Trump released his own in December, accompanied by a statement by a doctor claiming, “If elected, Mr. Trump, I can state unequivocally, will be the healthiest individual.”

The former first lady and secretary of State maintained her slim 2-point lead over Trump in our new tracking poll: 42 percent of voters back her while 40 percent back Trump; almost one-fifth (18 percent) of voters remain undecided. Clinton’s primary opponent, Sen. Bernie Sanders (I-Vt.), led Trump in the new poll 49 percent to 38 percent.

Voters were also asked to make their pick between Clinton, Trump and a potential third-party nominee, Libertarian candidate Gary Johnson. In that matchup, Clinton takes 38 percent of the vote, followed by Trump at 35 percent and Johnson at 10 percent. Seventeen percent of voters remained undecided.

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The 10 percent support for Johnson is about twice as high as most tracking polls from 2012, when he also ran for president against Obama and former Massachusetts Gov. Mitt Romney.

The Morning Consult survey polled 2,001 registered voters from May 19-23 for a margin of error of plus or minus 2 percentage points. See the toplines here and here, and the crosstabs here and here.