For a little more than an hour Thursday afternoon, the second floor of the Ronald Reagan Building in Washington, D.C., was Iowa 2016.

And if it's any indication, Sens. Rand Paul (R-Ky.) and Marco Rubio (R-Fla.) will give very different pitches to the Hawkeye State in one key area: foreign policy.

Sen. Rand Paul (R-Ky.). (Reuters/Kevin Lamarque)

About an hour after Paul delivered a wonky address to the Faith and Freedom Conference, arguing against sending money to conflict-ridden nations like Egypt and Syria, Rubio took to the same podium to argue that the United States remains the one country uniquely able to provide a guiding hand for the world.

Paul argued that the U.S. government is effectively funding a “war against Christianity” by sending money to people who have persecuted and even killed Christians; Rubio argued that if America doesn’t use its might and moral authority to prevent atrocities, nobody will.

The contrast was more in tone than in fact -- neither man dealt in too many specifics. But it does set up perhaps the biggest difference between two potential-to-likely 2016 GOP presidential candidates, and it just happened to occur in front of a room that closely resembled the all-important conservative Christian electorate in Iowa. (The Faith and Freedom Conference is put on by Ralph Reed’s Faith and Freedom Coalition – a major conservative Christian organization.)

Paul spent much of his time urging the United States to pull back from abroad, saying money shouldn't be sent to countries who are "burning the American flag" and saying anti-Semitic things.

“It’s clear that American taxpayer dollars are being used in a war against Christianity,” Paul said. "These countries are not our allies, and no amount of money is going to make them so."

Rubio, by contrast, used an extended biblical metaphor, labeling the United States the "salt of the earth" and offering what sounded like a pretty direct response to the Paul vision of foreign policy.

"This idea that somehow the time has come for America to retreat from the world and ignore the issues that are around that us ... we can't do that," Rubio said. "There is no other light. There is no other nation. There is no other example."

Rubio added: "I'm not advocating that Americans get engaged in every conflict on the planet and get involved in civil war. But there is nothing to replace us. I promise you it's not the United Nations. It's not China. It's not the European Union."

The two men, who were both first elected in 2010, have otherwise crafted very similar records in the Senate, with both ranking among the most conservative GOP senators according to most vote rankings.

The one area where they appear to be on different pages, though, is on issues of intervention. While Paul is very much straddling the line between his father’s brand of libertarian non-interventionism and a more pragmatic foreign policy, Rubio is carving out ground between the GOP’s recent interventionism and that same pragmatism.

Rubio in the past has allied with foreign policy hawks Sens. John McCain (R-Ariz.), Lindsey Graham (R-S.C.) and Joe Lieberman (I-Conn.) on Syria and more recently has pushed for arming the Syrian rebels and military action against Syrian leader Bashar al-Assad. None of those are things you'll see anytime soon from Paul, who has openly feuded with McCain and Graham over national security issues.

Judging by the receptions each man received Thursday, both messages have appeal to Christian conservatives. And that shouldn’t be too surprising; after all, Iowa was one of Ron Paul’s best states in the 2012 presidential race, which suggests there are plenty of libertarian-minded Republicans in the Hawkeye State.

Once the debate moves from speeches and broad ideals to specifics is when we start seeing some real differences between Rubio and Paul -- differences that could differentiate the two men from each other in a very significant way come 2016.

If, of course, both of them run.