So your claim is that Obama mentioned the word "terrorism" in his Rose Garden speech just in case in turned out to be terrorism and someone would try to call him on it at a later time?
To be fair, that might not be entirely without an element of truth, though I wouldn't put it quite that way. At the time, the White House was not in possession of enough information to definitively declare one way or the other whether it was a "terrorist" attack, defining that as an orchestrated attack by an organized terrorist group or groups. At the same time, it was appropriate that the President make
some remarks. With that in mind, a leader with experience should recognize that there are good reasons for being cautious about public statements issued early in the course of developing events -- and this is true whether he happens to be in the middle of a re-election campaign or not. His remarks have a way of turning into actual policy statements.
On the other hand, a mere
hopeful who has already made "Etch-a-Sketch" practically his middle name may feel that he can afford to be a bit more daring, especially if polls suggest that he has little to lose. He can stick his neck out with statements that are not well supported at the time by the sort of facts that can only be aquired through a full and detailed investigation. If he turns out to be wrong, many people will dismiss it as just ambition taking a shot anyway; you know: "Candidates say the darndest things".
After all, while it is not entirely beyond the realm of possibility that careless statements on the part of a mere candidate may actually
influence international events, it's certainly much less likely for them to do so in any significant way than is the case with careless statements by the person who already holds the official
title of President of the United States. Sure, he may aquire the occasional unflattering label like "Mitt the Twit", or draw sharp remarks from foreign leaders (which has to sting when it's coming from the leader of one of our closest
allies), or receive a TIC thank-you from the likes of Vladimir Putin for greasing the arms negotiation wheels for him by naming Russia as the "number one geopolitical foe of the US", but no one really takes that sort of thing very seriously, especially if they were watching the bizarre clown circus that was the race for the GOP nomination. I mean, who knows what might come out of the mouth of
any one of those nutjobs, right?
From a standpoint of game theory, I don't see the relative risks and payoffs being the same for a candidate as they are for a sitting President.