Newton Leroy Gingrich, a former college professor who co-writes speculative novels about alternative versions of history, has just coauthored the most momentous counterfactual of his career. Forget wondering what would have happened if the Confederates had won at Gettysburg, or if the United States had fought Imperial Japan and left Hitler alone: What if the two most absurd and most widely loathed candidates in last year's Republican presidential primaries had joined forces to win the White House?