Just agents or champions of change?

Sir Gideon Rachman writing about “Obama´s message to the world” January 8, refers to John McCain’s support of the Iraq war and though this is indeed an important fact on its own, I believe that much more important is that this support is given knowing that it is not a popular stance; and the same could be said about his full support of the recent legislation package on immigration. Therefore, and not that I do not like Obama, I do, but McCain seems also to be a valid candidate for “change”.

Why do not those both these candidates team up and propose what the American economy could need the most, namely a hefty tax on gasoline/petrol consumption? That would propel them from being merely agents of change into real champions of change.