Last night, newly ensconced Republican vice presidential nominee Paul Ryan sat down for his first solo interview with Fox News' Brit Hume and let slip an admission about Mitt Romney's budget plan -- an admission that's receiving surprisingly little press attention. Asked by Hume when the Romney plan would balance the budget, Ryan said he didn't know because “we haven't run the numbers on that specific plan.”

Thus far only a few media outlets have noted Ryan's comments. They include MSNBC's Morning Joe, which aired the clip three times, prompting Mika Brzezinski to quip that she hates it when people “don't run the numbers on the budget they propose.” CNN aired a clip of them last night on Anderson Cooper 360, and this morning on Starting Point host Soledad O'Brien said of Ryan's remarks: “He doesn't want to get wonky because he hasn't run the numbers because the plan is very vague.”

But there's been no print coverage, and no coverage on network news. Ryan's comments really should be getting more attention, for a number of reasons.

First, Mitt Romney has been going around telling everyone that, if elected, he intends to balance the federal budget by the end of his second term, or shortly thereafter. Ryan says that they don't know when Romney's plan will balance the budget. If Ryan is right, then what is Romney basing that claim on?

Second, the narrative that Ryan has cultivated among the press is that he's a budget wonk who understands fiscal issues and is allergic to deficits (this despite having voted for all the Bush-era policies that saddled us with high debt and ballooning deficits). Embracing the Romney budget and then saying that he doesn't know when it will balance because the campaign “hasn't run the numbers” runs counter to his reputation as a Serious Fiscal Hawk.

Third, as Ezra Klein of the Washington Post detailed yesterday, the Romney campaign's rhetoric about their budget goals butts up hard against fiscal realities. The campaign argues that their budget will cut spending to 20 percent of GDP by 2016. That's unlikely enough, but they've also announced that cuts to Medicare are off the table. As Klein put it, Romney's stated goal of balancing the budget in 8-10 years is “a fantasy, and it will never happen.” Ryan's remarks yesterday would seem to confirm that.

Fourth, how can you claim to have a budget and also to have not “run the numbers?” Isn't that all a budget is? Numbers that have been run?

The bottom line is that, by Ryan's admission, the Romney campaign is promoting a budget plan despite not knowing what it actually accomplishes. If that's not grist for the media grinder, then what is?