American Crossroads is out with this ad:

Now American Crossroads, like everyone else on the GOP side, knows President Obama is stuck with Joe Biden as his VP. But the ad, and others like it that are sure to follow, do three things.

First, just as Rep. Paul Ryan (R-Wis.) amplifies Mitt Romney’s brand — smart, serious, devoted to fiscal issues, cheery — Biden, if Republicans have their way, is being used to amplify the new Obama — nasty, indifferent to facts, willing to fan divisions. When you see ads with Obama campaign hacks standing behind Biden’s “y’all in chains” comment, you’ll know they are really trying to Bidenize the president.

Second, Biden didn’t just “happen” to Obama. He chose him and has stuck by him. Biden reflects Obama’s judgment and dispels the notion that the president wants the best and the brightest around him. Ole Joe doesn’t fit that description, does he?

And finally, Biden reinforces the perception that Obama of 2012 is not the hopeful, unifying figure he was in 2008. He is now about non-facts, slurs, attacks and divisiveness. In consultant-speak, Obama is ruining his brand. And Biden drives this point home every time he opens his mouth.

The double standard the media employs in covering Ryan and Biden is jaw-dropping but hardly unique in their campaign reporting. Biden can be the lovable uncle who says crazy stuff all the time. Oh, look how funny! Ryan is grilled and allowed no margin for error. But that’s fine. What we learned this week is that Ryan is up to being a heartbeat away from the presidency and Biden is not.