64% would seem to be enough of a plurality to say that America is ready for another party, but pragmatically what would that party look like? Historically third parties have arisen from the fringes of the existing parties with passionate voters who feel unrepresented by the existing parties. Such political movements are doomed to fail because they arise from an endpoint of the political continuum, and as such are appealing only to the few voters at that fringe, and very unappealing to at least half the voters from the other side of the spectrum. Ironically, the more successful the third party is, the more votes they siphon from the main-line party closest to them, the more likely they are to insure a victory for the main-line party most anathema to their positions.
I know much has been made of the Nolan Chart, which portrays the political landscape as non-linear, including axes for left/right, and for libertarian/statist. While this is an interesting exercise in determining political philosophy, it has little to do with political reality, as all but a few libertarians or statists continue to align themselves with either the Democrats or the Republicans as "the lesser of two evils". The most recent Gallup poll on the subject of political affiliation shows that 45% of Americans identify themselves as Republican/ Lean Republican, while 46% identify as Democrat/ Lean Democrat. That leaves just 9% claiming to be unaffiliated to be split between radical libertarians, anarchists, nazis, communists, those lying to the pollsters, the oblivious, and the disenchanted. This is hardly a cohesive unit, and politically it's probable that no one candidate could garner support from a major portion of this diverse 9%. A successful third party will need to attract voters already leaning toward one of the major parties.
If the fringes of the left or the right are not fertile ground for a successful third party run, might the center of political ideology provide a more promising avenue for success? Significant segments of both parties are repulsed by the extremes of their own party, just not as repulsed as they are by the extremes of the opposing party! If a third party could position itself in the center, might it be able to steal enough disenchanted voters from both parties to find victory? Such an attempt runs the risk of becoming neither fish nor fowl, and one way or another alienating everyone. "Moving to the center" is a successful strategy for candidates from major parties because they have the opportunity to pick up more independent voters without significantly risking losing their base at the extremes. A third party candidate would have no secure base, and would depend on the size of the center, the level of disgust with the existing parties, and its ability to remain ambiguous and nebulous on the issues to avoid offending potential voters. Such a candidate would probably need to be unaffiliated themselves, and yet experienced enough to merit election (think Jesse Ventura, or Michael Bloomburg). Charismatic enough to excite voters, yet undefined enough with references to terms open to interpretation that voters can project their own perspectives onto the candidate.
Generally, it's hard to generate a third party run for a candidate whose strength is in his blandness or moderation! So almost all of third party runs come from the fringes. I'm not saying that the fringes are always wrong, some of our greatest heroes have come from the fringes; they're just not popular. It's usually assumed that these third party type movements are co-opted by the major parties. The Tea Party is seen as an arm of the Republicans, while at least most of the proponents of Occupy Wall Street lean Democratic if they are political at all, and the party is clearly seeking to capitalize on the movement. However, in the "winner take all" system that exists, alliances are a pragmatic necessity, particularly with groups at the fringes. Localized elections are always more up for grabs, but the Tea Party will not soon run a successful candidate for President! Such a movement's greatest hope for "success" is to align with a party and move that party more toward the fringe. Some will say that this serves to alienate "the middle" where elections are won. Another way to look at it though is that a shift in ideology by one party, over time, particularly if it is a gradual shift, can actually shift the middle, the window of what is considered mainstream, also referred to as the Overton Window, in the direction of the fringe movement. The opposing party can enjoy short-term success by following this shifting window of the middle and leaning further from their base, or they can be true to their colors and try to drag the window back toward their side. This dynamic can be termed "polarization", which seems to be the dynamic currently most at work, except during elections when candidates must at least appear moderate to the ever larger segment of the population who don't see themselves at either extreme.
IMHO: Polarization increases the size of the bases, and the size of the middle, by dividing the electorate into more distinct groups. By so doing it creates a potential "base" in the center for a candidate charismatic enough to excite voters alienated by the extremes, yet remaining bland and indistinct enough to be inoffensive. Access to a lot of money goes without saying; a national crisis unresolved or perhaps exacerbated by the existing parties would help. Weak opponents and a platform that both intrigues voters and cannot be claimed by either mainstream party would be essential. In short, a successful third party run would require a perfect storm of national crisis, major party ineptitude, polarization, and a candidate who could excite the electorate with style over substance... I'm not sure that's a good thing, but it might be where we're headed!