One of Hillary Clinton’s key campaign promises is that she won’t raise taxes on the middle class.

In an Aug. 17 speech in Cleveland, the Democratic presidential nominee said, "I am the only candidate who ran in either the Democratic or the Republican primary who said from the very beginning (that) I will not raise taxes on the middle class."

Clinton began making that promise last fall, saying she would not raise taxes on those earning less than $250,000 a year. Analysts have said her proposed tax plan would have minimal impact on middle-income Americans.

However, Clinton is not the only candidate to make such a promise. In fact, we rated a similar claim by Clinton Pants on Fire in July. Our friends at the Washington Post Fact Checker gave the claim Four Pinocchios, its lowest rating.

We found that 13 of the 17 GOP candidates made promises last year that were far more encompassing than Clinton’s. They vowed not to raise taxes on anyone — including the middle class. Donald Trump was not one of these; more on this in a bit.

Twelve of the GOP candidates signed no-tax pledges with Americans for Tax Reform, a fiscally conservative group founded by Grover Norquist. They promised to "oppose any and all efforts to increase the marginal income tax rates for individuals and/or businesses" and "any net reduction or elimination of deductions and credits, unless matched dollar for dollar by further reducing tax rates."

The 12 signers were Ted Cruz, Marco Rubio, Rand Paul, Rick Santorum, John Kasich, Chris Christie, Bobby Jindal, Ben Carson, Carly Fiorina, Jim Gilmore,George Pataki and Rick Perry.

A 13th GOP candidate, Mike Huckabee, signed a personal oath to oppose all tax increases.

Two other Republican candidates had signed an Americans for Tax Reform’s no-tax pledge before last year: Lindsey Graham and Scott Walker.

So contrary to Clinton’s claim, 15 of the 17 GOP candidates had signed no-tax-hike pledges — not just on the middle class but everyone.

Who resisted?

• Trump, the GOP nominee, who said last year he didn’t want to sign the Americans for Tax Reform pledge because he "may want to switch taxes around."

• Jeb Bush, who said he objects to written pledges.

We searched debate transcripts and a variety of websites for any specific promises by Trump or Bush to shield the middle class from tax hikes, but we came up empty. Trump did, though, say in an Aug. 9 speech that he wants tax reductions for the middle class.

We made similar searches for the four Democrats who opposed Clinton during the primaries. While each of them spoke about the hardships facing the middle class, we found no evidence of them specifically promising to oppose tax increases on the middle class.

For our July fact-check, we asked Clinton’s campaign for an explanation of her and got a generic response. "Hillary Clinton’s policies, including her pledge not to raise taxes on the middle class, would build an economy that works for everyone, not just those at the top," Josh Schwerin, a campaign spokesman, replied in an email.

For this fact-check, Schwerin did not expand on his previous statement except to point out that some analysts have said Trump’s tax plan would most benefit the wealthiest Americans.

Our ruling

Clinton said, "I am the only candidate who ran in either the Democratic or the Republican primary who said from the very beginning (that) I will not raise taxes on the middle class."

Fifteen of the 17 Republican presidential candidates signed pledges not to raise taxes on anyone, which includes the middle class. Thirteen of those candidates signed the vow last year; the other two inked such a pledge earlier in their careers. Trump wasn’t one of them, but Clinton specifically mentioned the primary field. And that makes the claim both inaccurate and ridiculous.

We rate this claim, again, Pants on Fire.