If the GOP keeps losing, when would a viable replacement party emerge?

[Mister Mets]

The GOP's doing too well right now.

The party has majorities in Congress. In a horrible environment, McCain won 22 states and 45.7%.

They have to lose a lot worse for several cycles in order for a viable replacement party to be a possibility.

There would also be alternatives. The GOP could come roaring back after major losses if Democrats have a few bad breaks. But it would also be easier for Republicans to change than for someone else to replace them.

[Mister Mets]

It seems just as plausible to ask about Democrats.

It's conceivable that the party will have some bad breaks, especially with Republican advantage in Congress and the courts.

If a Republican wins in 2016 and does reasonably well in reelection in 2020, it'll likely coincide with the  party dominating redistricting.  And it's always possible the party will keep the White House in 2024 and later, either due to bad breaks or Democratic errors.

[Mister Mets]

It would be at least ten years after the GOP loses control of the House, and the Senate. That scenario is unlikely due to the party's edge in both (smaller states are slightly more Republican and the party does better in midterm elections so it's unlikely Democrats will take much of it, geographic sorting has favored Republicans in House redistricting.)

And during this long period, it's likely that Democrats would at some point screw up, allowing a new Republican to get elected to the White House.