Ask a political observer to name the front-runner in the Republican presidential primary—and after moaning about Donald Trump—they’ll probably offer one name: Sen. Marco Rubio.

It makes sense. Rubio is a strong political talent with a gift for rhetoric. He has an unrivaled ability to condense Republican Party ideas into soundbytes tied to his story and identity. He can segue from a capsule summary of his life—“As I’ve said many times before, my parents were never rich people”—to classic conservative rhetoric. “Here’s the best way to raise wages—Make America the best place in the world to start a business or expand an existing business.”

Rubio also sits well with most Republicans. The vast majority of Republican voters would support him in a general election, and he’s well-liked in early states like Iowa and New Hampshire. Other than immigration, where he faced conservative opposition in 2013, Rubio is close to a consensus choice for the GOP, well-placed to win the nomination.

But there’s a problem. In polling and in organizing, Rubio isn’t winning. In fact, he isn’t even close.