Because running on a platform of voting against a person is not enough to compel typically lazy Americans to come out to the polls. McCain (and now Romney) inspire nothing. To defeat Zero, we had better find another Reagan brimming with optimism and a clear vision, somebody who knows what we already know - that America is great country, blessed by God and the word's best Constitution, a people who's memory can be jogged to remember how to be great again - somebody who can convey that message to the apathetic middlings, and quick.
Somebody Insipirational, Intelligent, Charming, Faithful to the Creator, and Conservative.
Actually 132 million turned out to vote in 2008 compared to 122 million in 2004 and 104 million in 2000. McCain received 2 million votes less than Bush did in 2004.
The demographics of this country are rapidly changing. In 1988 minorities, as defined by the USG, comprised 15% of the vote; 19% in 2000; and 26% in 2008--based on exit poll data. By 2020, it is estimated that 34% of the vote will be minorities.
By 2023 half of the children under 18 will be minorities and by 2042 half of the country will be minorities. The US electorate is changing due to immigration and high minority birthrates. Immigrants and minorities vote Democrat.