If anything, Clinton/Obama is more like Brown/Cameron despite being from two opposing camps.
Brown was 'frontrunner' by default and was the party choice. The public took to him, and then he tanked (something Clinton has yet to do) when both his political style and his personal attitude began to turn off the voters. Cameron was seen as the young political lightweight. He got support and trust despite having few policies to begin with. These have been fleshed out as time progressed. Cameron makes direct moves into his opponents territory on poverty etc and makes some noises his own party didn't take to at first.
It was whispered and is now seen as close to the mark that David Cameron supports Obama. Perhaps not over the GOP field but he certainly has interest in him; an 'Obamacon'
No no no no no. Obama is a breath of fresh air, an embodiment of hope to sweep away the Bush years. Cameron? classic old-school tory who turns people off as much as he inspires. The only comparison is that he is a better speaker than Brown, but please don't compare him to Obama