Editor's note: Julian E. Zelizer is a professor of history and public affairs at Princeton University. He is the author of "Jimmy Carter," published by Times Books, and editor of a book assessing former President George W. Bush's administration, published by Princeton University Press.
Princeton, New Jersey (CNN) -- When George W. Bush finished his presidency, many observers wondered what the Republican Party would look like in the succeeding years. With Democrats in control of Congress and the White House, pundits declared the party was in crisis.
Republicans had become too comfortable with power, critics said. They had embraced the ways and means of Washington and were as enthusiastic about federal spending as their opponents. When the Tea Party emerged on the national scene, questions about the identity of the GOP only intensified.
Now that President Obama has officially announced his re-election campaign, it's time to see how his opponents will position themselves. As the candidates start to emerge for 2012, it is becoming clear that the potential contenders are embracing several different traditions and approaches to Republican politics.
First there is big business Republicanism. Former Massachusetts Gov. Mitt Romney best embodies the wing of the GOP that has championed the concerns of the business and financial community.
During the 1930s, NYU historian Kimberly Phillips Fein has shown, business leaders like the DuPont family mobilized to rail against FDR's regulatory initiatives. This faction of Republicans has usually challenged economic regulations and fought for tax reductions, though they have endorsed government subsidies that protect the corporate world.
Their basic argument is that government should not interfere in private markets and that government efforts to reduce inequality will fail. To some extent, New York real estate mogul Donald Trump, more a celebrity than a politician, is in this camp.
Another Republican tradition has been called conservative populism. Some Republicans have tried to appeal to working and middle class voters who traditionally voted Democratic, while supporting economic policies that are at least on the surface more favorable to upper income Americans. These Republicans have argued that limited government, balanced budgets, and traditional social values will ultimately strengthen America's middle class much more than government benefits.
Richard Nixon, who as a vice presidential candidate in 1952 defended himself from corruption charges by saying to television viewers that his wife didn't have a "mink coat" but rather had a "Republican cloth coat," was one of the most effective advocates of this view. As president, he appealed to the "Silent Majority" whose voices he said had not been heard in 1960s America.
Former Minnesota Gov. Tim Pawlenty, Indiana Governor Mitch Daniels, former Arkansas Gov. Mike Huckabee, congresswoman Michele Bachman and former vice presidential candidate Sarah Palin have staked their claims on these arguments. Pawlenty once said the GOP needs to become the party of "Sam's Club, not just the country club."
If the unemployment numbers continue to drop under President Obama -- and Republican governors continue to anger key middle class constituencies such as teachers and police by, among other things, seeking to restrict collective bargaining rights -- this will be a difficult sell. "Who are these evil teachers who teach your children, these evil policemen who protect them, these evil firemen who pull them from burning buildings?" the national president of the Fraternal Order of Police (a union which endorsed the Republican presidential candidates in 2000, 2004, and 2008), Chuck Canterbury, asked Politico.
A third form of Republicanism, the national security Republicans, have focused on the claim that Democrats are weak on defense for decades. While this was a central theme of George W. Bush's Republican party, there aren't many representatives of this ideal in the current crop of potential candidates other than Bush's former U.N. Ambassador John Bolton (he called President Obama's speech on Libya "pathetic").
Since Adlai Stevenson lost to Dwight Eisenhower, a military hero, in 1952 around a campaign that centered on communism, corruption and Korea -- some Republicans have repeatedly come back to this argument. Under President George W. Bush, national security arguments became a cudgel that was used to batter Democrats politically while the president was leading the "war on terrorism." The unpopularity of President Bush and the problems with the Iraq War raise big challenges for any candidate who wants to focus Republican credibility on this issue.
Yet another strand of conservatism is establishment Republicanism. Haley Barbour and Newt Gingrich best represent this tradition. In the 1960s and 1970s, Republicans could still claim to be something of an oppositional force in a Washington that was dominated by Democrats, but this has been a hard argument to make since Ronald Reagan became president.
Many Republicans in government -- such as former Vice President Dick Cheney -- are products of Washington even though they spend their public lives railing against the city. They came to rely on enlarged government to pursue their goals, whether using executive power to fight environmental regulations or congressional earmarks to win over constituents.
The struggle over the choice of a Republican candidate for 2012 will be a struggle over the identity of the party in the post-Bush era. Republicans don't have to choose one tradition over the other. Indeed, some politicians, such as Ronald Reagan, have brilliantly synthesized these themes together.
But right now there is no candidate of Reagan's caliber. This primary season will be an important one for the Republican Party in terms of explaining to Americans what the GOP is about and what exactly it would fight for if it gained back the White House.
The opinions in this commentary are solely those of Julian Zelizer.