If conservatives formed there own third party, which only supported Republicans with proven track records, members of Congress would have no alternative but to take the conservative position into account before supporting liberal legislation. The President would find his situation similar.
Consider the current election, if conservatives had hung together in declining to support Romney, he would b e making very overt guarantees to conservatives to get our vote. However, when so many automatically support him, no matter how dissatisfied they are, he knows he doesn't have to do anything - so don't expect anything.
The way the system is set up I'm afraid conservatives from the beginning were doomed to fight a delaying action against the inexorable growth of the State - it doesn't matter who we elect, all victories are temporary as everyone & everything is co-opted eventually.
How many times have we invested ourselves in a battle only to find the GOP had left us on the field.
Even so, I'm still inclined to focus the threat before me, and that is Obama, and hope for a little more time.
Honestly, the only other options are to revolt (and I mean really) or quit the whole thing and hope to escape the tender mercies of the State, in the form of death panels or whatever, for a few more decades until I go to my reward. I need a drink.