As the 2016 presidential hopefuls move closer to officially announcing, a new Gallup poll explores 16 top contenders' favorability ratings. Hillary Clinton is near the front of the pack, with net favorability of +11 — topped only by Dr. Ben Carson, who gets +12.

The major difference between Clinton and Carson, as you can see in this chart, is that Clinton is extremely well known — 89 percent of the public says they know enough to have an opinion on her. Carson, however, is one of the least-known candidates, with only 28 percent. The other candidates fall in the middle. Theoretically, this means the other candidates have more room to grow, since views on Clinton are set.

But often, potential candidates who aren't well known to the public start out with very few people disliking them. What's striking about this chart is that so few of the less well-known candidates this year start off with strongly positive net favorability.

For comparison, in a 2007 CBS poll taken as candidates were preparing to officially announce, Rudy Giuliani, John McCain, Barack Obama, and John Edwards all had net favorability exceeding +13, as you can see below.

This time around, no Republican except Carson scores even close to there, and the others fall into two groups. One batch starts off with slightly positive net favorability — this is Marco Rubio, Mike Huckabee, Jeb Bush, Rand Paul, Scott Walker, and Bobby Jindal. Candidates in the other group — Chris Christie, Ted Cruz, Rick Santorum, and Rick Perry — start off with more Americans disliking them than liking them, a tough hurdle to surmount.

Potential rivals to Clinton get little good news here. Even Elizabeth Warren starts out with a meager +3 net favorability, well behind Obama's +18 rating in 2007. The others — Joe Biden, Bernie Sanders, and Jim Webb — don't manage positive ratings at all.

It is worth noting that only part of Gallup's poll was conducted after the Clinton email story broke, so it's at least possible that a newer poll would find her ratings have sunk. But a Pew poll found that only 17 of respondents said they were following the email story very closely — and those were overwhelmingly Republicans and conservatives, who already dislike Clinton.