Nicholas Kristof is a columnist for the NYT.

...Newt Gingrich, Romney’s main rival for the Republican presidential nomination, is denouncing Romney with one of the ugliest slurs in the Republican lexicon: a Massachusetts moderate. Other moderate Republicans are savaged as RINOs — Republicans in name only — as if they emerged from an ugly mutant strain.

Yet, in fact, as a new history book underscores, it is the Gingriches and Santorums who are the mutants. For most of its history, the Republican Party was dominated by those closer to Romney than to social conservatives like Rick Santorum, and it is only in the last generation that the party has lurched to the hard right.

The new book, “Rule and Ruin,” by Geoffrey Kabaservice, a former assistant history professor at Yale, notes that, to compete in the primaries, Romney has had to flee from his own political record and that of his father, George Romney, a former governor of Michigan who is a symbol of mainstream moderation.

“Much of the current conservative movement is characterized by this sort of historical amnesia and symbolic parricide, which seeks to undo key aspects of the Republican legacy such as Reagan’s elimination of corporate tax loopholes, Nixon’s environmental and labor safety programs, and a variety of G.O.P. achievements in civil rights, civil liberties, and good government reforms,” Kabaservice writes. “In the long view of history, it is really today’s conservatives who are ‘Republicans in name only....