This deep division is driven, as was the case in the 1850′s, by fundamental differences in world-view regarding what this country is about.
There's something to that, but it's not quite the whole story.
Political parties are internally more homogenous and more polarized against each other than they were in the past. Conservative Southern Democrats and socially conservative Depression-era Democrats aren't really much of a factor. Nor are the socially liberal East Coast Establishment Republicans that prominent.
So partisan opinion about presidents of the other party is bound to be more negative than it was in the days where a large portion of each party was likely to be at least in part in sympathy with much of the worldview of the other party.
All the more so, since the "narrowcasting" brought about by the Internet and cable TV have altered our manners and behavior so much. Thinking the worst of the other party is the "new normal" and that is certainly different from how things were in the days of Ike and JFK.
But given that it is the new normal it's more chronic than acute, more a function of how things are than a sign of immanent breakup or breakdown. Given that enmity is an ongoing feature of the political scene, it's not necessarily true that people are angrier or more filled with rage, it may just be that we are more forceful in expressing differences that have been around for some time.
Of course a chronic ailment can worsen, become acute distress, and kill the patient. Something like that happened in the 1850s and may happen again. I'm not sure that 2012 will be the new 1860, though.
For one thing we know the main actors involved and know what to expect of them. In 1860, the first Republican president was something of a mystery and the uncertainty drove public fears to the panic stage, particularly in the South.
Also, we know that under usual circumstances what government can do it limited. We understand the checks and balances in the system prevent too much from changing too quickly. If Obama in 2009 and Bush in 2001 and Clinton in 1993, all with control of both Houses of Congress were only able to achieve limited results, it's not likely that whoever wins in 2012 will be able to radically change how things are.
Of course after long strain and tension, the ties that link us together could eventually snap, but 2012 isn't likely to be another 1860.