Democrats won both houses of Congress in the 2006 elections in part by arguing that Republicans were incompetent to govern. On immigration, they enjoyed a comparatively united party and cooperation from a Republican White House. More than any other factor, heat from the right killed the bill. But voters elect congressional majorities to solve problems, and Democratic incumbents can expect to pay some price every time they fail. But that fallout almost certainly will pale alongside the damage to future Republican presidential candidates. Hispanics represent the fastest-growing chunk of the U.S. electorate. Their choices help drive the rising swing states...