It used to be that candidates would make stump speeches and have debates, and that was the best guide you had to their intentions if they were to win—that, and their records. The latter consisted of the jobs they’d held and the actions they’d taken, and maybe a few major speeches they’d given.
But it would have been too much work to scour their every public utterance for errors or slips, or something they had said many years ago, before they were presidential candidates, that now could be used against them. Either the record didn’t exist, or it was too difficult to find and study.
But with the advent of the internet it has became a great deal easier. Now there are legions of hired hands, freelancers, and amateurs devoted to just that: the task of catching someone doing something that would turn the public against him/her. No matter if it’s twenty years or more ago, and they say they’re changed; it’s all grist for the gotcha mill.
Obama was more immune from that than most when he was running for president. It’s partly because he was the press’s darling, but it’s partly his own doing. It’s hard to escape the idea that Obama was purposely keeping a low profile and making sure he had as little a paper and video trail as possible, and that the record he did leave was as generalized and innocuous as possible, and that he had complete control of it (his books, for example). Maybe he knew even then that being too vocal or too well-documented could be used to damage a candidate and reveal him/her in unfavorable ways. And of course, the MSM has cooperated in keeping whatever record might exist as hidden as possible, if it could implicate Obama in a way that would reflect badly on him.
It’s a good thing Reagan’s candidacy was before the rise of the internet. Otherwise, we’d have probably been treated to videos of his old speeches praising Helen Gahagan Douglas, back when he was a liberal Democrat, in order to damage his conservative bona fides.