While much of their research is focused on America, they offer substantial evidence that this applies to all democracies, not just America. They devote substantial pages to Hitler's election in 1932/1933, and they refute the idea that the crucial surge of voters in 1932 were necessarily on board with much of the Nazi agenda. The voters were simply voting against those who held power in 1932.
Crucially, they point out, in every democracy, over and over again, the public will vote out the ruling party whenever the economy is bad. Therefore, the public does not seem to have any particular allegiance to any particular theory of the economy. Does socialism work? Does free trade work? Do markets work? The public doesn't seem to have much commitment to any of these ideas. Instead, when the economy is bad, the public will vote against whoever is in power, and they will vote for the other parties, regardless of what those other parties believe in, therefore, as they said, from the point of view of the people who run the parties, it is a game of musical chairs.
Consider this bit:
Page 205
A crucial feature of this brief litany of electoral responses to the Depression is that the ideological interpretation customarily provided for voters’ reactions in the United States does not turn out to travel well. Where conservatives were in power when the Depression hit they were often replaced with liberals or socialists, as in the United States and Sweden. But where relatively leftist governments were in power during significant downturns they were often replaced with more conservative alternatives, as in Britain and Australia. Where the existing party system was oriented around noneconomic issues, as in Ireland, voters rejected the “ins” and replaced them with “outs” whose policy positions cannot even be sensibly classified in left-right terms. Where the timing of elections forced more than one major party to stand for reelection during the worst years of the Depression, as in Canada and Sweden, voters seem to have been perfectly willing to reject both in turn. Where complex coalition politics diffused responsibility, as in France and Germany, discontented citizens turned to unstable coalitions, to fringe parties, or to the streets. Simply put, there is no consistent ideological logic evident in voters’ responses to the Depression when we look beyond the American case. When voters got a chicken in every pot at election time, they usually liked the incumbent party’s ideology just fine, whatever it happened to be. But when incomes eroded and unemployment escalated, they became ripe for defection to anyone who promised to bring home the poultry.