President Barack Obama may be an excellent communicator but he faces a serious challenge in that department from incoming U.S. Sen. Marco Rubio, argued a prominent communications expert on Wednesday.

Maintaining that the best communicator has prevailed in every presidential election since 1980, Brad Phillips released a study Wednesday looking at the communication skills of Obama and 18 possible Republican opponents, including Rubio and former Gov. Jeb Bush. Phillips, a former journalist with CNN and ABC News, is the founder of Phillips Media Relations, a firm specializing in communications training, and is a prominent blogger. 

“Most pundits analyze a general election by looking at the same old measurements, such as unemployment data, consumer confidence, and early polling,” said Phillips. “But they always miss a reliable predictor: the more gifted media spokesperson has won every presidential election since the beginning of the 24/7 media age in 1980.”

Phillips maintained that the winning presidential candidate in the general election always had a clearer message and was more charismatic, articulate and optimistic than his opponent. Philips also stressed that candidates who spoke candidly and “appeared most comfortable in his skin” prevailed at the  ballot box.

“Although we tend to complain about the length of presidential campaigns, the reality is that nonstop media exposure to candidates gives us a good sense of who they are,” insisted Phillips. “That’s important, because many voters – especially the crucial independents – base their votes on their personal comfort level with a candidate, not specific policy positions.”

Phillips assigned grades to Obama and the potential Republican candidates, but noted that with more than a year until the Republican primaries and almost two years till the general election, the grades were not final.

Phillips awarded Obama an A in the 2008 campaign but gave the president a C in his most recent report.

“I suspect the president will raise his communications game during the 2012 election just as he did in 2008,” noted Phillips, who pointed to the president‘s handling of health-care issues back in August 2009 as when Obama started losing momentum. “And he appears to have started turning the corner on delivering his message more effectively. But his grade is based on where he is now, not where he could be on Election Day 2012.”

Rubio was the only potential Republican candidate who earn an A from Phillips.

“Rubio is a media trainer’s dream,” noted Phillips in his evaluation of Rubio. “When asked to speculate, he refuses. When given an opportunity to slam the president, he passes, thus denying the reporter an off-message sound bite. When asked about his opponent’s motives, he refuses to characterize his opponent’s thinking and instead articulates his own.”

Right behind Rubio with A- grades were former Arkansas Gov. Mike Huckabee, who ran for the Republican presidential nomination back in 2008, and Mississippi Gov. Haley Barbour.

Bush joined a pack of Republicans in earning a grade from Phillips in the B range. While Gov. Chris Christie, who looks very unlikely to turn, earned a B+ and U.S. Sen. John Thune of South Dakota earned a B from Phillips, Bush joined former Massachusetts Gov. Mitt Romney and Gov. Bobby Jindal of Louisiana, who has said he has no interest in running, with a B-.

“Mr. Bush would fare well in a general election,” insisted Phillips. “He has a clear message, uses everyday language, appears comfortable in his skin, and wraps his views around an optimistic vision of our nation’s future.”

But Phillips also saw problems with Bush deciding to follow in his father’s and brother’s footsteps.