Just speaking to the motivation of those servicemembers, I believe the 2008 election was an anomaly. Obama garnered so much hype which led to his large amount of support from ethnic minorities within the Armed Forces, and then there was a combat veteran and former POW in McCain, who was seen as the logical successor to Bush as Commander-in-Chief. Now you have an unpopular incumbent, and an even less popular challenger--neither with military experience, and both seemingly out of touch with the realities faced by those in uniform. For these reasons, among others, I feel this disconnect lends credence to the servicemember's perception of the politician paying nothing more than lipservice to the magnitude of their sacrifice.
"The rich man writes the book of laws the poor man must defend, but the highest laws are written on the hearts of honest men."