1. Depressed rural turnout. Part of that might be population loss. Some areas in the midwest had counties flipping from Obama 08 to Romney, but had less actual votes for Romney than McCain.
2. Severe bluing in inner cities. Michigan's map was about a normal map for a 3% loss, not a 8% loss. Was it fraud? Probably some in the cities like normal. $20 says it's in the absentees.
However, it is myth that McCain garnered more votes than Romney as can be verified here.
Just three examples:
Nationwide: Romney 60,932,235 vs. McCain 59,950,323
Michigan: Romney 2,115,256 vs. McCain 2,048,639
Pennsylvania: Romney 2,680,433 vs. McCain 2,655,825
Pathetically small differences, for sure, given ObaMao's four years of misrule. Plus considering that BO dropped from 69.5 million voters in 2008 to 65.9 million in 2009, an opportunity lost partially due to poor turnout for sure. But also outright fraud of a magnitude even more sophisticated than 2008, when certain Philadelphia precincts did not produce 72K votes for BO versus 0 for McCain.