The political significance of Mitt Romney’s hidden tax returns almost certainly has to do with his tax rates. The Republican frontrunner has been reluctant to admit he pays much lower tax rates than middle-class workers, despite the vast wealth he made during his vulture-capitalist career.

It was noteworthy, then, that Romney managed to tell the truth this morning. “What’s the effective rate I’ve been paying? It’s probably closer to the 15% rate than anything,” Romney said. “My last 10 years, I’ve — my income comes overwhelmingly from some investments made in the past.”

The politics of this are awful for the likely GOP nominee. Working families probably won’t be amused to learn Romney — the guy who got rich laying people off, and has been a professional candidate for the last six years — pays a lower tax rate than they do. They’ll be even less pleased to know Romney, if elected president, will fight to keep it this way, even when he calls for tax increases on those struggling most.

What’s more, while Romney’s candor was a change of pace this morning, as Paul Krugman and Jamison Foser explained earlier, we still need to see those tax returns.

But Romney said something else at the same event that’s worth remembering.

Mr. Romney added: “And then I get speaker’s fees from time to time, but not very much.”

In fact, in the most recent year, Mr. Romney made $374,327.62 in speaker’s fees, at an average of $41,592 per speech, according to his public financial disclosure reports.

There’s some dispute about the precise figure from Romney’s disclosure forms, but at a minimum, he earned $362,000 in speaking fees last year.

In Romney’s mind, that’s “not very much” money.

For a candidate already accused of being an out-of-touch elitist, unaware and unconcerned about the struggles of working families, this is clearly another “uh oh” moment.

As American Bridge joked, for most of us, “not very much” refers to money “found in the couch.” For Romney it means over $360,000.

This is the same guy who recently suggested elected office is only for the rich, thought nothing of dropping $10,000 on a bet during a debate, and considered a $1,500-a-year tax cut for the typical middle-class family to be a meaningless “band aid.”

Remember when Rachel Maddow compared Romney to Thurston Howell III? It was well grounded.

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Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.