The failure of any Republican candidate to make the case for vigorous American leadership in the world during last week’s Republican presidential debate has sparked a debate in Washington: Is the Republican Party becoming increasingly isolationist, as Sen. John McCain suggests?

Perhaps. A recent Pew Poll found the proportion of conservative Republicans who support U.S. activism in world affairs has fallen by 19 points since 2004, with a majority of conservative Republicans now saying that America should “pay less attention to problems overseas and concentrate on problems here at home.”

But there may be other factors than a new isolationism at play. The erosion in support for U.S. engagement abroad could be the result of a strong “recession effect” (when the economy isn’t doing well, Americans of all political stripes tend to want to be more attentive to problems at home). Moreover, for GOP voters there could also be an “Obama effect,” as Republicans grow increasingly dissatisfied with the president’s doctrine of “leading from behind” on the world stage.

This seems to be the case when it comes to Libya. A recent Fox News poll found that just 29 percent of Republicans favor the current U.S. involvement in Libya. But the same poll also found that the vast majority of Republicans believe Obama has not laid out a clear objective in Libya, and 51 percent of Republicans would favor the mission if the goal was “to immediately remove Muammar al-Qaddafi from power.” In other words, a majority of Republicans support a more vigorous mission in Libya if we set a clear goal of “regime change” – hardly a sign of growing GOP isolationism.

But even those Republicans who oppose the Libya intervention under any circumstances cannot be rightly called isolationists. Libya clearly is a “war of choice” and the decision whether or not to support military action there is not an easy call. I have argued that the U.S. has important interests in removing Gaddafi, but this view has been contradicted by none other than Obama’s own secretary of defense, Robert Gates, who publicly declared that America has no “vital national interest”at stake in Libya. It is hard to accuse Republicans of isolationism for opposing a conflict where the administration waging it says no vital U.S. interests are on the line.

Contrast the GOP skepticism of the Libya mission with the much stronger Republican support for the war in Afghanistan – where our interests are clearer and the execution of the mission appears to be stronger. Despite the collapse of popular support for the war effort on President Obama’s watch, Republicans remain the only group in the country where a majority still say the Afghan war is worth the costs. When the House nearly passed a resolution setting a fixed timetable for withdrawal from Afghanistan last month, just 26 Republicans joined a nearly united Democratic caucus in voting for retreat. That’s too many, to be sure, but it not exactly an indication that isolationist sentiment has overtaken the Republican Party. Indeed, GOP support for the Afghan mission remains strong despite the fact that our ally there is a corrupt government whose leader has made clear he is ungrateful for the blood and treasure we have spilled.

The fact is, Americans have always been reluctant internationalists. This is particularly true of conservatives, who are the inheritors of what historian Walter Russell Mead has called the “Jacksonian tradition” in American politics – ready and willing to do whatever it takes to defend the United States but deeply skeptical of the pet schemes of the foreign policy elites. Maintaining popular support for American interventions abroad, particularly in tough economic times, requires presidential leadership. The commander in chief must be willing rally the country in support of foreign interventions – explaining U.S. interests, laying out a clear strategy, and asking Americans for their support. This is something President Obama has manifestly failed to do.

In the GOP debate, we saw a similar failure of leadership on the part of the Republican candidates. Not one stepped forward to argue for success in Afghanistan or to lay out a vision for a vigorous conservative internationalism – and some, like Mitt Romney, pandered to perceived isolationist sentiment by talking withdrawal instead of victory. This is troubling. Because so little was said on foreign policy in the debate, it is hard to tell whether this is a sign of resurgent isolationism or simply political opportunism. But this much is certain: It would be disastrous for the party, and the country, if those seeking the Republican nomination decided to that the best path to presidency was to claim the mantle of Pat Buchanan instead of the mantle of Ronald Reagan.

In his farewell address to the 1992 Republican convention, Reagan rejected what he called the “new isolationists” and gave his party this advice: “Whatever else history may say about me when I’m gone, I hope it will record that I appealed to your best hopes, not your worst fears, to your confidence rather than your doubts.” When it comes to America’s engagement in the world, that is good advice for the current GOP field.