The nation still moving away from Republicans demographically, too. It can't be emphasized enough that Michael Dukakis would have won the 2008 election. His exit polls of 40% among whites, 89% among African-Americans, and 70% among Latinos is enough to reach 50%+1 now, even in the event that African-American turnout was only 12% of the vote instead of 13%.
From our analysis of the Current Population Survey post-election supplement, here are our estimates for voter turnout in 2008: 76.4% white, 11.9% black, 7.4% hispanic, 4.3% other, with the categories defined as mutually exclusive (for example, if you're white and hispanic, you count as "hispanic"). The exit polls say 74% white, 13% black, 9% hispanic, and 5% other (not adding to 100% because of rounding error), but I think CPS is more trustworthy.
Now we can take the Dukakis numbers and plug them into the 2008 turnout numbers, as long as we make some estimate for the votes of "other." I'll assume 55%, halfway between his performance among whites and among hispanics. (By comparison, we estimate from the Pew pre-election polls that Obama got 45% of the two-party vote among whites, 96% among blacks, 68% among hispanics, and 59% among others.)
Plugging in Dukakis's percentages by ethnic group and using the turnout numbers of 2008, we get a national adjusted Dukakis vote of .40*76.4% + .89*11.9% + .70*7.4% + .55*4.3% = 48.7%, which is better than the 46.1% he actually received but not quite enough to win.
This doesn't really shoot down Bowers's main argument--demographic shifts are important. I think he was overstating his case just slightly.
And, yes, I know that if Dukakis had really been running in 2008, things would've been different. I'm just following Bowers in using the Dukakis vote as a handy way to summarize the trends, keeping voting by ethnic group constant. Voting by ethnic group is not constant (as we can see by comparing Obama's breakdowns to his predecessors), but doing this sort of calculation is a good way to visualize the demographic changes that are occurring.