How to explain the rejection by American Democrats and British Labourites of center-left strategies that recently proved so successful?
One explanation is that people are acting out of principle. Left-wing Democrats and Labourites love to hear candidates echo those of their beliefs they know to be unpopular with the wider electorate. (Right-wing Republicans love this too.)
Another is that today these parties have not been chastened by repeated defeats. Republicans held the White House for 16 of the 20 years before Bill Clinton won; Conservatives held Number 10 Downing Street for 18 years before Blair did. Partisans were willing to accept half a loaf in those circumstances, perhaps less so today.
A third explanation applies specifically to center-left parties, including Dangerfield’s Liberals a century ago. They were bedeviled by demands from different constituencies — Irish Catholics, feminist suffragettes, militant union leaders — which their compromising tendencies could not assuage. Liberal Britain faced internal violence, Dangerfield argues persuasively, when it unexpectedly went to war in August 1914.