Republicans face a tricky situation when it comes to making the case against President Obama heading toward November: How to persuade voters not to vote for a president who is viewed favorably by a majority of adults, including key independent voters?

Sen. Marco Rubio (R-Fla.). (AFP/Getty Images — Jewel Samad)

The answer, at least according to Sen. Marco Rubio (R-Fla.) in several recent appearances, appears to be to make the case to those voters that Obama may have been an inspirational figure four years ago, but he’s not the same person today.

An address by Rubio in South Carolina over the weekend was the latest instance of the Florida freshman senator and rising GOP star heaping praise on the Obama of 2008, then pivoting to attack the Obama of 2012.

“For all the policy disagreements that we have with our president, it is hard to understate how much he inspired people across this country four years ago,” Rubio told South Carolina Republicans at a fundraising dinner in Columbia, according to CNN’s Peter Hamby.

Rubio went on to argue that the present-day Obama “is a very different person” and that “we have not seen such a divisive figure in modern American history as we have over the last three and a half years.”

The argument echoes one the potential Mitt Romney running mate has made in recent weeks. In an interview on “Fox News Sunday” earlier this month, Rubio contended that “all of the things that made (Obama) different and special four years ago are gone.”

“He was going to be a post-partisan uniter to bring Americans together,” Rubio said. “And three-and-a-half years later, the president has become just like anybody else in Washington, D.C. And in his obsessive effort to win his reelection, he has lost himself and he has lost what makes him different.”

The White House’s politicization of the successful bin Laden raid, Rubio said, was “one example about how his administration has become just like everybody else.”

It’s a different argument than the one the Florida Republican was making earlier this year. In a late January interview on CNN, Rubio argued that “no candidate in American history has ever run more negative ads than Barack Obama” — a claim that Washington Post Fact Checker Glenn Kessler awarded one Pinocchio.

A look at recent polling provides some context as to why Rubio may be shifting his rhetoric.

In a mid-April Washington Post-ABC News poll, 56 percent of all adults said they viewed Obama favorably. That includes 53 percent of independents, a constituency that will be the key to winning the White House.

Rubio is perhaps in a better position than some other potential running mates to make the case that Obama has been in Washington too long.

The freshman senator, who was elected in the 2010 tea party sweep, is at 40 years old among the youngest members of Congress. And as the debate over federal student loan rates has heated up in recent weeks, he has also gone out of his way to note that he believes he is “one of the only senators here who still has a student loan.”

By praising the Obama of 2008 and then taking a dig at the 2012 Obama, Rubio appears to be focusing his efforts on swaying those voters who may be disillusioned with the president four years after his historic victory.

Will his effort pay off? We’d like to know your thoughts; the comments section is open for business.