If I made this a multiple choice question, most people might expect something like Which president does not belong on the list with the others?, with the answer being B.
That's because we tend to do our analysis of politicians primarily in terms of policy positions.
But FDR, Reagan, Clinton, and Obama represent logical points along a continuum of politicians who succeeded because they were absolute masters of controlling the media narratives of their day. When you look at these four--not in terms of ideology, but in terms of media mastery--you discover a very interesting evolution.
FDR existed at the dawn of mass media as we know it. Take two specifics of his media persona: (1) his mastery of the Fireside chat represented an awareness of the influence of radio as a popular media that no other politician of his day ever really grasped; and (2) his ability to keep the print media from showing photographs of him as a cripple [which is the term that would have been applied in that milieu] gave him a control of his visual image that no other politican in pre-TV days ever achieved.
Interlude: Kennedy v Nixon [TV is a different medium; always wear the make-up].
Reagan understood the power of limited, stage visual media (film, television in the infancy of cable before the 24/7 news cycle had developed) that allowed him to control the image of him as a person or even as a character playing a role in such deft fashion (until the last two years of his second term) that his policy positions and even policy reversals literally did not significantly impact public perception of him as a positive figure. Reagan drove journalists nuts, because the man he successfully projected in the media was not the man they saw every day, and--ego being what it is--they never understood that the man whose intelligence they deprecated had played them.
Clinton arrived at the early peak of the 24/7 cable news cycle and the very beginning of the internet as a popular media. But the 24/7 news cycle had much more dominance than the "new media" during his presidency. The Clinton War Room approach was the first to consciously use the strategy of a defined media narrative and the saturation of the available media outlets with talking heads using common talking points. Moreover, even though Clinton never managed to become a speech-maker of the FDR/Reagan class, he was an excellent communicator and outdid both of his predecessors in the arena of improvised cut and slash.
But what's really telling about Clinton--or perhaps about the age in which we live--is that his implicit understanding of media was obviously so dated by the 2008 primary cycle that his old tactics seriously wounded Hillary's campaign. Clinton, ironically, presided over the birth of the new media, but clearly does not understand how it works. It's actually kind of scary that media now changes so fast that Bubba's grasp of the media became completely obsolete in just 8 years.
Obama's relatively short pre-presidential political career was actually a tremendous advantage, as he didn't have anything to unlearn: virtually all of his political career has existed in the YouTube, Facebook, blogosphere world. He understands, for example, that the 24-hour reaction time of the Clinton years is now hopelessly slow, and that sound-bites have now shrunk to Twitter length.
It is critically important, from an historical and not a political perspective, to note that FDR, Reagan, and Clinton all demonstrated their mastery of the existing media forms of their day, and that the end of each of their administrations roughly coincided with watershed changes in media that prevented anybody else from repeating their performances. TV became the dominant media after WW2; cable news became dominant only toward the end of the Reagan years; the new media arrived only at the end of the Clinton years.
Individuals do adapt to changes in media types. The fact that Barack Obama has successfully melded the political killer instincts of his Clinton hold-overs with the new media savvy of his own people (think: the exquisite marginalizing of, first, Sean Hannity and now Rush Limbaugh, who represent some of the last dinosaurs of Clinton-era media trends) is indicative that we may have the first administration in place that not only understands the media of its day, but also understands and adapts to media evolution over time.
This is critical because media has not stopped and will not stop evolving. I'm not good enough to tell you what will replace the Drudge/kos, YouTube, Facebook/MySpace, Twitter milieu of today, but I can tell you without fear of contradiction that 2014 the politicians positioning themselves for 2016 will exist in an entirely different communications world.
That's why, IMO, there is structurally nobody on the GOP side--policies aside--who is able to compete, because in terms of media Rush Limbaugh really is the best they've got, and he's outdated by ten years.