Too many other ads "diminish effectiveness," said Steve Lombardo, a veteran Republican strategist who worked on Romney's 2008 presidential run. When ad buys are made outside the campaign, "there can't be the same level of discipline when it comes to overarching strategy," he added.
In recent weeks, for example, ads by Americans for Prosperity hit Obama on failing to fix the economy, while the Republican Jewish Coalition attacked his policies on Israel and Crossroads GPS asserted that middle-class taxes would go up because of Obama's healthcare overhaul.
There's another disadvantage to leaning too heavily on outside groups: After Labor Day, their dollar doesn't go as far.
Under federal law, TV stations must offer candidates the lowest available rate for airtime, a deal not available to political parties and outside groups. As available TV time shrinks in key states and prices rise, a campaign dollar thus goes further than a dollar from an independent group.
Super PACs have proved themselves adept at negative advertising. But they are less helpful when it comes to advocating for Romney's candidacy. Because outside groups cannot coordinate, the candidate cannot speak directly for himself in ads run by his allies.
"That leaves outside groups little choice but to run ads that contrast the opponent," said Todd, the GOP ad maker, who is not affiliated with the Romney campaign. "But the case against Obama's presidency has been made and accepted. The thing that Romney needs to do is make the case for Romney. The best person to do that is Mitt Romney."