Mine are anti-vax and climate change denial. When 100% of the smartest people in the world agree with one side of an issue and then you take the other side I don't trust you to make any important decisions that affect me. What are your positions?
If you really believe that "100% of the smartest people in the word" believe that manmade carbon emissions are causing significant "climate change" and "warming," you're a fool.
As for my litmus test, here are my disqualifications:
1. Abortion: People who are broadly pro-choice (not just minor exceptions for rape, incest, and "life of the mother" - I'm talking about the people who are generally Ok with slaughtering babies at pretty much any time before birth for any reason, which is evil)
2. Climate: Global warming "truthers" (such as SD and 42) who refuse to acknowledge the serious debate over mankind's role in "climate change."
3. Immigration: Anyone who advocates for open borders or broad amnesty (I will at least consider, but not favor, a candidate that would supposedly allow amnesty on strict conditions)
4. Fiscal Policy: Anyone who doesn't care about the national debt, or believes that we can meaningfully reduce our deficits with tax increases.
5. Foreign Policy: Anyone who thinks we can actually trust countries like Iran to honor agreements, or is naive enough to believe that we can actually monitor Iran's compliance under the current framework.
6. Healthcare: Anyone who advocates for single payer or heavier reliance on insurance and restricting consumer choice (like Obamacare).
7. Energy: Anyone who wants to increase subsidies for wildly impracticle and ineffecient "green energy" like wind and solar (I'll allow sucking up to Iowa corn growers because, otherwise, that would disqualify pretty much all the candidates).