Refusing to vote for somebody [edited] just because they don't line up with your view of a sin issue such as abortion, imo, smacks of the self-righteousness Paul wrote about in the first part of Romans chapter 2.
The simple truth is this: each of the candidates for President are SINNERS!! Totally depraved! As such they SIN! Whether this is supporting abortion, or saying whatever it takes to get elected, then going ahead and doing what they wanted to do all along. How do you quantify sin? If you try to, then I submit you need to study Romans 2 more completely.