It’s not so much in the top-line results of the polls, although he has bumped up to the first tier in the very early going, as the other questions that show he has considerable room to grow his level of support. Consider the new WSJ national poll. On the basic ballot test, Jeb Bush leads (23 percent), with Rubio second (18 percent). But if you combine the first and second choices of respondents, Rubio tops everyone else at 41 percent. Also, 74 percent of respondents said they could imagine backing him, the best finding for any of the candidates. If you combine this broad openness to his candidacy with his evident talents as a candidate, you see why it’s almost become a cliché to speak of Marco Rubio’s “upside.”