In a hypothetical third-party system, you'd have a robust third party full of Ron Pauls (and, perhaps, Buchanan-brigaders and Tancredoites as well). Would this party be a majority? Probably not. But it could, under parliamentary practice, form a coalition with the mainstream Republicans and force them to adopt most of their platform if they wanted a majority. Ditto for the DemoRATS regarding any Green-type party.
Paddy Buchanan & Ron Paul are against the war.
If that is what you want, just vote Democrat.