With Perry sinking like the Dow, a less desirable outcome's odds are rising. Rick Perry would have been the ideal nominee to sober up and thereby sever the contemporary GOP -- permanently.
If Mitt Romney wins the nomination, as is now likely, the far right, also known as the Tea Party, will scream that the party's candidate lost to President Obama only because the party failed to nominate a true conservative (which in reality Tea Partiers wouldn't know from a Bolshevik). This disgruntlement over what they'll interpret as a lost opportunity will motivate the extremists to remain in the two-party system and work to further radicalize the Republican Party, especially for 2016. Some will splinter off in 2013, if not before, yet enough could easily remain entrenched in the GOP to hold the party line farther to the right.
A Perry nomination, on the other hand, would serve up all the far-right radicalism the radicals could ever want. The above excuse-making would be invalidated. And in the bloody aftermath of a Perry-led GOP's crushing defeat to Obama, the party's moderates -- and they are out there -- would coalesce to brutally oust the extremists. Thus the creation of a more structurally cohesive Tea Party of the formal third-party species. In other words, political irrelevance and permanent obscurity.
Either route, however, poses a long-term danger to the Democratic Party. The party would weaken in the absence of a strong, unified opposition, as American political history has repeatedly shown. It will take time for the GOP to reorganize and resettle itself as a respectable party of authentic conservative grounding; and in that time the Democratic Party, too, will further splinter.
It's as plain as reading a road map.