In theory, a 3rd party vote would be great! Government's supposed to govern as a collective body, working together for the common good, and if they see a lot of people voting for a separate party they'd want to try and represent everyone's interests as much as possible when you're sending the message that you don't care for either of the two main parties in power.

In practice, the two parties are so entrenched that they just laugh at, and proceed to ignore third party vote data. They only care about a) people who are fence sitters, and b) getting people to vote (or in the Republican case, doing everything possible to prevent their enemies from voting).

You'd have to actually build up a second conservative party from scratch to the point where it can legitimately threaten the Republican party as a spoiler candidate. Much easier said than done, and doesn't fix the underlying cause of the problems in the first place, since a conservative could then do the same thing with a more liberal party as a front. The real solution is to use a system that is immune to spoiler parties (also referred to as clone candidates, candidates similar to one another that they pull votes away from each other in a plurality system).