The only slice of the population that I can realistically see rioting at this point, are those terminally dependant on welfare. If any candidate cuts the flow, he will know it in the streets.
It may be heresy to say this here, but I don't think that the economy is the weak point of the Obama admin. The entire world has been suffering from a series of financial meltdowns that occured around the globe, and that were largely independent of political parties and ideology. What we are experiencing is IMO one of the first waves of failure of the globalized economy, and the risky market gambling and poorly thought-out "products" of the financial industry. I don't believe that it's something Obama or Romney can easily fix.. It's essentially a structural problem, in that we have restructured the way in which we think that national and global economies should work, but the truth is that they can't work this way.
We cannot have a global economy without either elevating all poor nations to our level, or allowing first-world nations to sink to the level of poor nations. There is no way for wages to equalize, unless we bring everyone to the same generally poor standard of living. But wait, then there is no longer any advantage to globalization, because there are no longer any exceptionally cheap workforces available to take advantage of. The advantage of poor third-world labor doesn't last forever - eventually they demand higher wages and to be on equal footing with, say Americans, British, French, etc.
Capitalism is not meant to operate on a one-world economy. It requires trade & competition between entities operating sovereign in different nations. The only way it can "work" (poorly) is if it's forced, i.e. fascism, global government - getting into tinfoil territory here.
I actually don't blame the democrats for the state of the economy. Can they do better? Sure. But... The buyout of the auto industry that was started by Bush and carried on by Obama is something that many people are angry about that I think is an example of tough economic decisions that had to be made that saved a ton of jobs. Romney would've probably just let GM & Chrysler hang, throwing thousands of jobs to the wind. Do I know that? Nope, but it jives with his history and actions as a manager in Bain. Romney prefers to let enterprise fail & pick up the pieces for his own benefit.
There are plenty of other reasons not to like Obama that we are all pretty well aware of.
My problem is, I won't be happy with anyone who's elected. I don't like Obama or any of his cabinet members, their policies, and the causes they like to get behind and push. I also don't like conservatives who lean towards war-mongering and base policy on religion and make-believe visions of Rockwell-esque Americana, mom's apple pie, etc. Democrats and republicans, anyone who plays by the party rules, they all leave a foul taste in my mouth. Where are all of the moderate politicians that are willing to work together, like they used to in America's strong days, beyond simple lip service given to compromise & unity?
THAT'S why I think we are in serious trouble. It goes beyond one candidate. It's a game now on which party will win - the winner is never us as a whole.