Single Issue voters
I contend that voters on the political extremes tend to make a voting decision based on one single issue. Using the right to life vs abortion issue as an example I venture to say that as many as 40% of voters will vote based upon this single issue. It will not matter if you consider yourself a liberal or a conservative, this issue controls your vote. There are several other issues that control votes (probably to a lesser extent). Examples are: gun control (for some conservatives), climate change (for many liberals), etc.
It does not really matter if a candidate is unethical, immoral or incompetent as long as he or she adopts a position that agrees with the single-issue voter. It doesn’t even matter if the candidate really believes in the position, it is enough that he or she publicly adopts the stance.
This situation further enhances the increasing polarization that is contaminating our political process. There are many issues that we can come together on: Healthcare reform, budget control & reform, infrastructure improvement/ maintenance, etc.
Single issue voters are a reality and I think there is little that can be done to mitigate their numbers. It’s a political reality that most candidates recognize. The task then becomes to determine what will appeal to the majority of the remaining voters.