Rom 3:8 And not rather, (as we be slanderously reported, and as some affirm that we say,) Let us do evil, that good may come? whose damnation is just.
The apostle Paul says in Romans that those who “do evil that good make come” are worthy of condemnation (damnation). As Christians, one should not vote for John McCain, who supports killing babies whose mothers have been raped or whose parents are related, such that Obama, who supports killing babies for any reason whatsoever, would not win.
Likewise, we should never rape another human being, even if it would save the whole world. God never authorizes us to make moral compromises.
Mat 16:26 For what is a man profited, if he shall gain the whole world, and lose his own soul? or what shall a man give in exchange for his soul?
Predicting the future is a hard task. We can never know what harms or evils might be brought into the world through our compromises, but we can know for certain that never doing evil will always be the right thing.
We do not vote for McCain/Hitler (fill in your politician) so Obama/Stalin won’t win.
We do not kill an innocent baby so that baby doesn’t grow up in an unloving environment or so some woman does not have to live with reminders of traumatic events.
We do not rob from the young to pay for the health care of the old. (Remember God labeled even a 10% flat tax as an evilly oppressive tax rate. 1Sa 8:15)
We do not forbid trade with foreigners such that natives will have higher paying jobs.
We should not illegalize smoking so people might live longer.
We should not do evil that good may come.