"The question is, are religious leaders overstepping their bounds in doing this?"

Yes! Nothing turns me off faster than my religious leaders trying to shove me in one direction or another. They should talk about religion and values (perhaps even issues, eg: with pro-life causes), but elections are outside their realm of expertise. Telling me that I should support a candidate or party based on theology is ludicrous. I have studied political science, I inform myself about the candidates' positions, and I make sure I vote in every election. The decision I make is up to me. I will be the one discussing it with God if the issue ever comes up (though I doubt it will) and I'm not about to defend someone else's conscience.