Editor's note: Julian Zelizer is a professor of history and public affairs at Princeton University. He is the author of "Jimmy Carter" (Times Books) and of the new book "Governing America" (Princeton University Press).
(CNN) -- Mitt Romney spoke this weekend to the students at Liberty University, a hotbed of conservative studies,and he has been forced to think about his ties to the right. He is facing a difficult challenge in determining what his relationship should be with the tea party Republicans who helped revitalize the GOP after the doldrums of 2008.
Although there are more conservative Republicans grudgingly endorsing Romney and polls show that more tea party activists are coming to accept Romney as their candidate, there is strong evidence that there remains a great deal of distrust, which could dampen enthusiasm on the campaign trail and create tensions if mishandled. According to Congressional Quarterly, Texas Rep. Louie Gohmert told reporters, "I am not as excited as I am desperate" to elect someone other than Obama.
Any misstep could cost Romney the election. If Romney is seen as too close to the tea party, he could easily undercut his ability to win independent votes in the swing states that will determine the outcome of the election.
If Romney distances himself too much from the right wing of the party, he might dampen the enthusiasm that he needs to organize, to raise money and to make certain that people come out on Election Day in what promises to be a close election.
The challenge facing Romney is not new to Republican candidates. Indeed, every Republican who has won office since the middle of the 20th century has confronted this dilemma. Each successful candidate has handled the challenge in a different way.
One model has been for candidates to completely distance themselves from the right and to instead allow the vice presidential candidate to focus on appealing to the base, to act as an "attack dog." This is what the military hero Dwight Eisenhower did in 1952 when he avoided associating with the McCarthyite wing of the party that was ramping up Cold War rhetoric. Instead, Gen. Eisenhower let Richard Nixon do the dirty work, calling Democratic candidate Adlai Stevenson "Adlai the Appeaser" and tagging liberal Democrats as being a step away from communism.
The Eisenhower model would be difficult for Mitt Romney to follow. In the modern media age, especially after the Sarah Palin fiasco, there will be immense attention on whoever runs with Romney. If he selects a right-wing nominee, the kind of scrutiny he or she will receive could easily overshadow Romney's campaign and any effort he hopes to make to appeal the center.
The second model is Barry Goldwater's full embrace of extremism in 1964. Taking on President Lyndon Johnson, Goldwater ran as a true conservative who espoused right-wing values and had no interest in compromise.
Goldwater used bold rhetoric, taking on programs like Social Security and the Tennessee Valley Authority, demanding radical cuts in government. When liberal Republican Nelson Rockefeller spoke at the Republican convention, the delegates booed and jeered. When Goldwater spoke, defending extremism, they burst out in applause. Goldwater doubled down with his vice presidential running mate, New York Rep. William Miller, who further solidified Goldwater's image as the candidate who was far to the right.
This model would certainly not work for Romney, who would come off as disingenuous. Romney has spent too much time positioning himself as a pragmatist and moderate to make this kind of move. Trying to pull a Goldwater would only play into the accusations that he is a candidate without a core.
The third option is the George H.W. Bush model. In 1991, Bush, who was not at all comfortable with the right wing of the party and never got the "vision thing," ran a slash and burn campaign in 1988 that focused on devastating the record of Massachusetts Gov. Michael Dukakis. Without fully embracing conservative ideals, Bush's campaign revolved around the depiction of his opponent as unpatriotic, as an extreme liberal and as someone not fit to be in office.
While the strategy worked for Bush, it could be insufficient for Romney, who faces a much tougher opponent in President Obama, whose personal favorability ratings remain high and who has much stronger backing from his own party. The president won't be as easy to tear down. If Romney simply goes negative as a way to avoid dealing with the right wing of his party, his campaign could fail.
The final model is the one used by Richard Nixon, Ronald Reagan and George W. Bush. Each of these candidates did send clear signals to the right that they would be an integral part of the coalition. None of these candidates fully distanced themselves from right-wing forces, yet their campaigns focused on broader themes that were attractive to a much bigger part of the population. Nixon spoke of law and order in 1968, Reagan talked about anti-communism and private markets in 1980, while Bush emphasized "compassionate conservatism" in 2000.
This final strategy is the best path available to Romney, because it will allow him to send signals to the right that he understands what they are about and will be part of their coalition, while offering themes that can win over the rest of the GOP and perhaps even disaffected Democrats.
The problem is that thus far Romney has struggled to find those themes. Thus far he has focused mostly on castigating President Obama. In the next few months leading into the Republican convention, he will have to lay out one or two broad themes that can extend his reach well beyond the right without alienating them. This is a difficult task and one that has been challenging to many Republicans. But doing so will be essential to handling the tea party Republicans, who pose a massive challenge to his campaign.
The opinions expressed in this commentary are solely those of Julian Zelizer.