"And, indeed, as recently as 1988 one could have witnessed moderate Democrat Joe Lieberman successfully challenging incumbent liberal Republican Senator Lowell Weicker with the support of, among others, William F Buckley, Jr.
"But it turns out that Lieberman vs Weicker was something of a dying gasp of a political order that was rendered obsolete by the civil rights revolution. Twenty years later we find ourselves several congresses into a brave new world in which every single Democratic Party legislator is to the left of every single Republican Party legislator. In terms of partisan politics, in other words, we’ve become a normal country. But as Linz observed, the “normal” outcome for a country with our political institutions and ideologically sorted parties is constitutional crisis and a collapse into dictatorship.
"So far it hasn’t happened here. The 1998-99 effort to impeach Bill Clinton was sufficiently unpopular that moderate Republicans wouldn’t vote for it. Al Gore chose not to contest the legitimacy of the Supreme Court ruling that handed the White House to George W Bush despite the fact that the electorate preferred Gore. And by 2007-2008, Bush was so unpopular that the Democratic Party leadership felt the wisest course was to avoid provoking a crisis and basically just wait him out. But we live in interesting times…" --Yglesias.