A majority of Americans now believe "the U.S. will ultimately succeed in achieving its goals" in Iraq, according to the Pew Research Center. I imagine UK voters would be at least half as pessimistic as that, judging by the unceasingly negative media coverage and a poll this time last year showing that a puny 5% of Britons felt safer as a result of the war.
The Politico translates this into "Support for war effort highest since 2006". If that's an accurate way of reading it, McCain's unwavering stance on the war will continue to benefit him.