Late last week, Karl Rove’s attack operation, Crossroads GPS, launched an aggressive new ad campaign, targeting President Obama on the economy. Though the total price tag for the offensive is $20 million, the first wave is a $5 million ad buy in 10 states.

Crossroads, of course, is a leading Republican Super PAC, collecting undisclosed funds for exactly these kinds of efforts. As part of the Democratic effort to level the playing field, a rival operation, Priorities USA, unveiled a response to the Rove ad overnight.

YouTube video

For those who can’t watch clips online, the spot calls the Rove ad “politics at its worst,” before telling the viewer that Republicans have “opposed economic reforms at every turn,” crafted “a plan that would essentially end Medicare,” and want to “slash education while giving huge tax breaks to Big Oil and the wealthy.”

The ad concludes, “We can’t rebuild America if they tear down the middle class.”

It’s a good ad, but the larger point to keep in mind is that the ad exists because Dems are choosing to play by the same rules Republicans play by. I can appreciate why this is controversial for some leading progressive voices, but without Priorities USA, it’s likely the Crossroads ad would simply go unanswered right now.

I’m of the opinion that the national discourse doesn’t benefit from these new campaign-finance rules, but the discourse also suffers when only one side follows the rules to get its message out to voters.

That said, it will remain a huge challenge for Democrats to try to keep up. While the first wave of Rove’s ads will come from $5 million in secret donations, the new Priorities USA spot will be backed by a $750,000 buy. Crossroads’ commercial will air in 10 states; Priorities USA’s ad will run in five states (Colorado, Florida, Iowa, North Carolina, and Virginia).

Presumably, if Priorities USA receives a strong response and a bunch of new contributions come in, the effort can be expanded, but it’s worth remembering that even if Dems commit wholeheartedly to fight fire with fire, Republicans will almost certainly have a bigger flame-thrower.

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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.