The candidate: Barack Obama

The ad: In the new spot, "former President Bill Clinton takes center stage," says Ashley Killough at CNN. The high-profile Obama surrogate speaks directly to the camera, telling voters, "This is a clear choice." (Watch the ad below.) Clinton derides the Republican plan "to cut more taxes on upper income people and go back to deregulation. That's what got us in trouble in the first place." The nation's 42nd president then says Obama "has a plan to rebuild America from the ground up, investing in innovation, education, and job training." Before signing off, Clinton reminds Americans of his own presidency, arguing that the economy "only works if there is a strong middle class. That's what happened when I was president. We need to keep going with [Obama's] plan."

The ad buy: The 30-second spot will air in several key swing states: Virginia, New Hampshire, North Carolina, Florida, Ohio, Iowa, Colorado, and Nevada. The Obama campaign has not made the amount of the ad buy public.

The strategy: By tying himself to Clinton, Obama is clearly trying to "portray his clash with Romney" as a choice between a return to the popular Clinton's record of "strong economic growth" and a re-run of "George W. Bush's approach to governing," which, as Clinton suggests, "got us in trouble in the first place," says Olivier Knox at Yahoo News. Indeed, the goal is to "transfer positive feelings voters have about the economy under Mr. Clinton to Mr. Obama," says Laura Meckler at The Wall Street Journal. Also, says Greg Sargent at The Washington Post, Clinton is implicitly making the case — without even mentioning Romney — that the GOP candidate "doesn't have the answer." And the timing of the ad is no accident, says Maggie Haberman at Politico: "Clinton is now making this pitch ahead of the Republican National Convention, where his name is sure to come up again."

The reaction: "Don't look now," says Taylor Marsh at her blog, "but the presidential election of 2012 has a shadow candidate." Because Obama has failed to "turn around what he inherited" or "articulate a Democratic economic message that sings, it's up to William Jefferson Clinton to do the job he can't." Hey, ease up, says Doug Mataconis at Outside the Beltway. "This is a very good ad." It'll likely play well for Obama in swing states. "There is, of course, always a risk when one puts Bill Clinton out there that he'll steal the spotlight," but all told, "this strikes me as a smart move on the Obama camp's part." It is smart, says Sargent, and subtly reminds voters that while they may be "disappointed that [Obama] hasn't lived up to expectations," he's still better than Romney. Maybe, says Peter Grier at The Christian Science Monitor. But "given a continued flat economy, it's possible that this approach reflects a subtlety that will be lost on many voters."

Sources: ABC News, CNN, The Christian Science Monitor, Outside the Beltway, Politico, Taylor Marsh blog, The Wall Street Journal, The Washington Post, Yahoo News

See more campaign ad analyses:

-American Crossroads' "Smoke"

-Romney's "A Better Day"

-Obama's "Revealed"