I want to ensure that I am demonstrating my non-partisanship. Hence, I will post a commendation on John McCain and a defense of some of the compromises he had to make.
John McCain has had more real life experience on the issue of the treatment of POWs than any canidate out there. That has helped him formed a much better moral judgment on the way we conduct this war (note: this does not excuse him for cupably giving Bush congressional approval for going into Iraq). He has helped pushed interrogation reform (including revising the Army Field Manual) and the Military Commissions Acts. Now, both pieces of legislation are improvements over what was (or what failed to be) in place, and showed his willingness to critique the administration of basic human rights.
Unfortunately, like with so many issues in this messy business we call politics, he had to compromise. Bush and the administration opposes restrictions and oversight over its (unjust) conduct of the 'war on terror.' Failing to even try to give lip service to Jesus' injunction to 'love your enemies' (at least even to respect them as human), he resisted efforts to ensure that Bush abides by just laws. Hence, even though both bills represent improvements; there are still major flaws.
Unfortunately, compromise is necessary for improvement. McCain had to compromise to pass these improvements. I think McCain, if elected, will continue to improve our treatment of our enemies (and work to apply the rule of law to them). Of course, so will Barack Obama; however, McCain, as de facto leader of the Republicans, will be able to use the added clout to push his party (it would help, and be morally obligatory, for evangelicals to ensure that they side with and pressure McCain to continue in that direction).
Politics is messy, and both canidates are pushing for changing their party (Obama in taking seriously religious concerns and inserting "reducing abortions" in the party platform- with help of evangelical Tony Campolo and McCain in ensuring we are conducting this war ethically). In both canidates we have a much better pick than between Kerry (or Gore) and Bush; and both canidates, to various degrees, come closer to Christian values. However, both canidates also have serious flaws (McCain about Iraq, Obama about abortion). Christians could, in good conscious, vote for either one AS LONG AS THEY CONTINUE TO PRESSURE BOTH TO WORK FOR JUSTICE.