Julian Zelizer: New Hampshire was the Key Test for Romney

(CNN) -- The New Hampshire primary will tell us a good deal more than the Iowa caucuses did about where the Republican candidates stand and how they might do in the general election against President Barack Obama.

While the unpredictable nature of the Iowa caucuses offered Rick Santorum an opportunity to shine, Tuesday's vote will tell us where the party is really headed, in what has been a Wild West of a presidential selection process, one with more ups and downs than the Colorado Rockies.

The New Hampshire primary, established in 1916, has a long and treasured history in American politics. It has often been the site where new voices have been able to upset the status quo and take on establishment figures.

In 1952, the military hero Dwight Eisenhower successfully challenged "Mr. Republican" Robert Taft, the senator from Ohio, who was thought to be one of the strongest figures in the party. That same year, Tennessee Sen. Estes Kefauver shook up the Democratic Party by winning a stunning victory against President Harry Truman, fueling his decision not to run for re-election.

In 1968, Minnesota Sen. Eugene McCarthy's strong second-place showing similarly upset President Lyndon Johnson, forcing him to think twice about how strong his support was within the Democratic Party. The results, Sen. Ted Kennedy recalled, demonstrated that "overnight, Johnson had become beatable." A few weeks later Johnson told the nation that he would not run for re-election....