Mitt Romney may not be ready for prime time. But he is finally getting ready for Sunday morning.

After avoiding the Sunday morning talk shows during the primary campaign—when he pretty much stuck to the friendly confines of the Fox News studios—Romney is branching out to do CBS News’s Face the Nation.

For Romney, this is a significant step, an acknowledgement that he is running for president of the United States, not for president of the Republican Party.

No major party nominee in modern history has earned his nomination with no narrow an appeal to the great mass of American voters as Romney.

George W. Bush, despite his many challenges, was far more accessible to mainstream media outlets in his 2000 presidential run than has been Romney. And Ronald Reagan regularly appeared on a variety of programs. The same goes for Democratic contenders. (Barack Obama even did Fox News Sunday during his primary run in 2008.)

Romney’s been a rare hothouse flower, sheltering himself from the scrutiny that past contenders have seen as a necessary part of the process. When he has exposed himself to even minimally tough questioning—remember the interview with Fox’s Braier?—Romney has melted down. Badly.

“This is the kind of setting Romney tends to steer clear of,” notes Politico’s Maggie Haberman. But it is the kind of setting that presidents must master.

So Sunday becomes a bigger test for Romney than just another interview. He’s entering the real world of presidential politics. And it remains to be seen whether he can cut it.