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Hillary Rodham Clinton opened another front in the ad war today, joining rival Barack Obama on the air in Indiana with a new TV spot (subscription) featuring the endorsement of Evan Bayh, the state's junior senator and a frequently mentioned candidate to be Clinton's running mate.

In the ad, which consists almost entirely of Bayh speaking directly into the camera, the Indiana senator touts Clinton's toughness, particularly on the economy, and runs through a number of her campaign's key message points.

"We need a leader who'll fight for good jobs, change trade deals like NAFTA, cut taxes for middle-class families," he says. "Someone who's ready to be commander in chief from Day One." Bayh also notes the two decades he's known Clinton -- a personal touch that validates his judgment of Clinton's character while recalling her argument that she is the most experienced Democrat in the presidential race.

Clinton has used a similar advertising strategy in previous contests: Her campaign ran an ad (subscription) before the Ohio primary featuring the endorsement of former Sen. John Glenn. But the newest spot's no-frills approach and praise for Clinton's "spine of steel" most recall a John McCain ad from December called "Backbone Of Steel" (subscription), in which major league pitcher Curt Schilling endorsed the Arizona senator.