Interpreting the meaning of election results is difficult. Voters weigh multiples issues that do not aggregate well. Sometimes they vote for a candidate because they prefer her policies and sometimes they vote for a candidate because they dislike the other candidate. Best I can tell, the only consistently valid interpretation is that candidate X received more votes than candidate Y. Nothing more, nothing less.
Obama received more votes than McCain. But does this imply a mandate for change as suggested here? I do not know but I doubt it. Consider the following. Assume there are approximately 220 million voting age adults in the US. Obama received approximately 62 million votes. Therefore, only 28% of the electorate voted for Obama. 72% of the electorate did not support Obama. Furthermore, how many people voted for Obama because they associated McCain with Bush? That is, how many people were indifferent to Obama but wanted to punish Republicans. Any number greater than 0 reduces support for Obama’s proposed change. Of course, some people who support Obama did not vote because they expected Obama to win so they allocated their time to something else. But is this 32% of the citizenry so as to push his support to 50%? I doubt it.