McCain is the one that gets quoted, rather than Obama, because there's a public perception that McCain's threat is more sincere than Obama's. There's a commonly held assumption that Giuliani's threat is more credible than Edwards', because Rudy has a background as an uncompromising street fighter (albeit against crime in New York). Giuliani and the Republicans will use perception to their advantage: Even today, this tough-guy image makes the Republican Party more acceptable to voters when it comes to fighting terrorism.
So, yes, they all want sanctions, and they all believe that no option should be taken off the table—McCain, Giuliani, Romney, Clinton, Obama, and Edwards have all said as much. But you have to ask yourself how much you believe them. If the public keeps believing that the Republican candidates have more of the toughness that's needed to execute the policy, then the Republican strategy is working better.