Paul Krugman defends one of the claims in his book:
White male math, Paul Krugman: So, people ask why, in The Conscience of a Liberal, I downplay the role of issues other than race in swinging the political balance in favor of the GOP. The answer, basically, is the math: once you take the great southern switch into account, there isn’t much left to explain.
In some correspondence with Larry Bartels, whose “What’s the matter with “What’s the matter with Kansas?”" is must reading for anyone trying to understand modern American political, economy, the issue of how the Democrats lost white males came up. Larry points out that you really need to separate out the South. Here’s what he had to say:
Unless you have a peculiar nostalgia for the racially coercive Democratic monopoly of the Jim Crow era, it makes sense to focus on the rest of the country. There, the Democratic share of the two-party presidential vote among white men was 40% in 1952 and 39% in 2004.
White men didn’t turn against the Democrats; Southern white men turned against the Democrats. End of story.
Here's the abstract from the Bartels article along with the table showing the numbers Krugman is referring to. The discussion surrounding the table is also included:
What’s the matter with “What’s the matter with Kansas?, by Larry Bartels: Abstract: Thomas Frank’s What’s the Matter with Kansas? asserts that the Republican Party has forged a new “dominant political coalition” by attracting working-class white voters on the basis of “class animus” and “cultural wedge issues like guns and abortion.” My analysis confirms that white voters without college degrees have become significantly less Democratic; however, the contours of that shift bear little resemblance to Frank’s account. First, the trend is almost entirely confined to the South, where Democratic support was artificially inflated by the one-party system of the Jim Crow era of legalized racial segregation. (Outside the South, support for Democratic presidential candidates among whites without college degrees has fallen by a total of one percentage point over the past half-century.) Second, there is no evidence that “culture outweighs economics as a matter of public concern” among Frank’s working-class white voters. The apparent political significance of social issues has increased substantially over the past 20 years, but more among better-educated white voters than among those without college degrees. In both groups, economic issues continue to be most important. Finally, contrary to Frank’s account, most of his white working-class voters see themselves as closer to the Democratic Party on social issues like abortion and gender roles but closer to the Republican Party on economic issues.
And on to table 1:
Table 1 provides a different way of looking at the growing electoral importance of income differences within Frank’s white working class. The rows of the table present separate tabulations of changing Democratic support over the whole period from 1952 through 2004 among voters in the upper, middle, and lower thirds of the income distribution in each election year. The first entry in the first column of the table,−5.9, represents the overall decline in Democratic presidential support among white voters without college degrees over the 14 presidential elections covered by the NES surveys. ... Reading down the first column, we see that the decline in support for Democratic candidates was much greater – almost 15 percentage points – among the most affluent members of this group (with family incomes in the top third of the national income distribution). On the other hand, the Democratic vote share among the least affluent members of this group (those in the bottom third of the national income distribution) actually increased by almost five percentage points.
It should be clear from these comparisons that material economic circumstances have become more important, not less important, in structuring the presidential voting behavior of Frank’s white working class over the course of the past half-century. While it is true that Democratic presidential candidates have lost significant support among this group, those losses turn out to be heavily concentrated among its middle- and upper-income segments, and indeed have been partially offset by increasing support for Democratic candidates among working-class whites with low incomes.
Whereas the rows of Table 1 differentiate Frank’s white working-class voters on the basis of income levels, the columns present separate tabulations of changing Democratic support for the South and for the rest of the country. These separate tabulations suggest a third and even more striking lacuna in Frank’s account of the decline in Democratic support among white working-class voters over the past half-century. Focusing on the overall trends, in the first row of the table, we see that the Democratic presidential vote share has declined by almost 20 percentage points among southern whites without college degrees. Among non-southern whites without college degrees it has declined by one percentage point. That’s it. Fourteen elections, 52 years, one percentage point.
The remaining entries in the table provide similar comparisons of southerners and non-southerners within each income segment of Frank’s white working class. In every case, we see a similar 20-point gap between the South and the rest of the country. Among the most affluent segment, the difference is between a substantial ten-point Republican shift outside the South and a massive 32-point Republican shift in the South. Among the least affluent segment, a ten-point Republican shift in the South has been more than counterbalanced by an 11-point Democratic shift in the rest of the country. (On the other hand, within each region we see a similar 20-point difference in the shifts observed among voters in the top and bottom thirds of the income distribution; the economic and regional trends are largely independent and both quite powerful.)
To a good approximation, then, the overall decline in Democratic support among voters in Frank’s white working class over the past half-century is entirely attributable to the demise of the Solid South as a bastion of Democratic allegiance. In the first half of the 20th century the historical legacy of the Civil War and the contemporary reality of Jim Crow racial politics induced southern whites to maintain “unquestioning attachment, by overwhelming majorities, to the Democratic party nationally” (Key 1949, 11). However, dramatic action on civil rights issues by national Democratic leaders in the early 1960s precipitated a momentous electoral shift among white southerners (Carmines and Stimson 1989), eventually replacing an anomalous Democratic majority with a much less anomalous Republican majority.