Marco Rubio, who announced his bid for the presidency on Monday in a call to donors, has been called the “best communicator” in the Republican Party. Over and over and over again.

But he has little to show for it.

He enters the fray with surprisingly low support. Despite four years of national prominence, he has averaged 6 percent of the vote in primary polls over the last few months. That’s the same or worse than five candidates who are thought to have a much smaller chance of winning the nomination: Ted Cruz, Rand Paul, Ben Carson, Mike Huckabee and Chris Christie. Mr. Rubio is acceptable to many but, so far, the first choice of few.

Mr. Rubio’s struggle to break through is a powerful reminder that winning a presidential primary is not just about skill as a politician. It’s about positioning, and Mr. Rubio, at the moment, is in a much worse position than many assessments of his political talent would suggest. In basketball terms, he’s boxed out.