I find it rather comical. In 2000 Bush was effectively appointed by the Supreme Court, after loosing the popular vote nationwide and winning the Electoral College mostly due to shenanigans perpetrated in Florida. In 2004 Bush did appear to win the popular vote, barely, as well as the Electoral College. However, it was mostly due to some very significant electronic voting irregularities in Ohio. If he hadn't carried Ohio he would have lost. After both these suspect elections Bush declared he had a mandate.
Yet with Obama, after winning both his terms quite handily, you deny him the same standing.