Reason #4 - McCain's Choice of Palin as Running Mate
John McCain's choice of ultra-conservative Alaska Governor Sarah Palin as his running mate energized the Republican religious right base and significantly increased McCain's campaign trail crowds and enthusiasm, a segment of voters already on-board the Republican ticket, albeit somewhat reluctantly.
The political problem is that, by early October 2008, more than 50% of independent voters had an unfavorable impression of Palin. And by all reports, Palin's unfavorable ratings have grown since then.
Further, per Times magazine, 45% of all women, including conservative women, view Palin "unfavorably," versus only 27% of all women voters who view Democratic vice-presidential candidate Joe Biden "unfavorably."
In its October 17, 2008 endorsement of Obama for President, the Washington Post wrote, "The choice is made easy in part by Mr. McCain's... irresponsible selection of a running mate who is not ready to be president.
"... we find no way to square his professed passion for America's national security with his choice of a running mate who, no matter what her other strengths, is not prepared to be commander in chief."
The obvious bottom-line is this: for many reasons, snarky, outspoken Sarah Palin was a disastrous running-mate choice by McCain if he intended to attract additional voters and supporters beyond the traditional Republican base.
For more, see McCain Campaign Hurt by Selecting Palin as Running Mate.
(Also read Five Reasons Why Obama Will Win the '08 Election.)