There is one hiccup in your theory, and that's the phenomena of the single-issue voter. For many people here at THR, the 2nd Amendment is everything. Many of us (and I'm purposely generalizing here) will not vote for a candidate who isn't strong on the 2A front no matter how much we might align with said candidate's remaining platform. There are many people in America who feel the same way about some other issue. For example, try getting someone who is "pro-choice" to vote for a pro-gun candidate who is not pro-choice. Not going to happen.
This is the problem with the left/right paradigm. The parties have aligned themselves with certain voting blocs that are intended to be mutually exclusive. The pro choice voter can't possibly vote for a pro gun candidate, even though the two issues aren't really connected.