QUOTE OF THE DAY…. Throughout July, Republican leaders were aggressive in touting their belief in the Tax Fairy — there’s no need to worry about paying for tax cuts, because they magically pay for themselves. It was a startling example of “invincible ignorance,” but from the Senate Minority Leader to unelected GOP candidates, this was the official party line.

This morning on MSNBC, House Minority Whip Eric Cantor (R-Va.) accidentally noted the truth about Republican demands to extend Bush’s tax cuts. Host Savannah Guthrie asked Cantor if he would “simply acknowledge that passing these tax cuts worsens the budget deficit problem.” Cantor dodged, arguing that people don’t want to see “a tax hike.”

So, Guthrie tried again, asking if Cantor “had any dispute with the notion that it does exacerbate the deficit picture.” The Republican replied, “What I said in the beginning is, um, if you have less revenues coming into the federal government, and more expenditures, what does that add up to? Certainly you’re gonna dig the hole deeper. But you also have to understand, if the priority is to get people back to work, is to start growing this economy again, uh, then you don’t wanna make it more expensive for job creators.”

That’s quite a concession. Cantor is willing to admit that tax cuts would “dig the hole deeper” when it comes to the deficit — a fact that’s consistent with common sense, but which Republicans have fought vehemently for a month — but believes the economy is more important than the deficit.

Oddly enough, I consider this something of a breakthrough. For 18 months, Democrats, most notably President Obama, have said the deficit matters, but the state of the economy matters more. Republicans and their Tea Party base have argued the opposite, insisting that the deficit has to take priority; we’re facing a debt crisis; etc.

Cantor’s line, repeated as if it were obvious, puts Republicans in a different place — if boosting the economy means “digging the hole deeper,” so be it. I happen to agree wholeheartedly.

At this point, then, it’s time for a different debate. For a year and a half, it’s been economic growth vs. deficit reduction. Cantor is signaling a new argument — economic growth through spending vs. economic growth through tax cuts.

Instead of arguing over whether to increase the deficit, Cantor seems prepared to concede the point, and argue deficit increases are unfortunately necessary. Democrats should welcome his new-found wisdom, and initiate a discussion over the efficacy of spending vs. the efficacy of tax cuts.

Since we already know we get a much better bang for the buck when it comes to spending, it’s an argument Republicans will lose, at least if reality had any bearing on the outcome of policy debates.

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.