Here is a fact of life, with the obvious divide in this Nation, such as it is, we can’t trust that our vision is shared by the majority in this country, and getting worse every election..
It is clear that the majority favors repeal of ACA "Obamacare" and are against legalization of illegal aliens.
Thus, there is no litmus test in this, there is only an issue of integrity in the faithful representation of a majority of voters.
Should any special interest place itself between voters and their elected representatives, using coercion or bribery, then there is a litmus test to the elected representative from that special interest.
Have you noticed how the GOpe is proclaiming that we have to jettison almost every plank of our platform to be competitive with Democrats. Nevada GOP just too opposition to abortion and sodomite marriage out. The national GOP is fighting for amnesty harder than they ever fought against CommieCare, and harder than they ever grilled Holder and the IRS on high crimes and misdeanors. It looks like they are actively, consciously working towards having one party in all but name, and perhaps soon enough, even in name. The more they move left, the more we follow, and even run ahead of them on some things.