Why Pete Buttigieg's Iowa surge was not surprising

(CNN)South Bend, Indiana, Mayor Pete Buttigieg surged 16 points to land at top of the Democratic field in the latest CNN/Des Moines Register/Mediacom Iowa caucuses poll.

Sometimes a climb in the polls for a candidate is surprising, but in the case of Buttigieg, you could see the potential a mile away. Why?

It all has to do with the fact that a lot of caucusgoers had and have a highly favorable view of Buttigieg. As I've stressed over and over again, the key in caucuses and primaries is to be loved, not liked. It doesn't really help a candidate if their somewhat favorable rating is high. They want their very favorable rating to be high.

Buttigieg's very favorable rating was 33% in September. That was good enough for second best in the field, even though he was fourth in the horserace at 9%. When the very favorable rating and horserace don't match up for a candidate, it's a sign that a candidate's fundamentals are either significantly stronger or weaker than the horserace number implies. In Buttigieg's case, it was the former.

CNN's latest Iowa poll: Live analysis on Buttigieg surging to first place

The Buttigieg bump is reminiscent in this way of Sen. Elizabeth Warren's from June to September. In June, she had the best very favorable rating of all the candidates. Yet, she was 8 points behind former Vice President Joe Biden in the horserace. By September, she was at 22% to Biden's 20% in the horserace.

Today, Buttigieg's 25% in the horserace looks a lot more like what we'd expect given his current very favorable rating of 42%. If anything, he's running slightly better than we might expect.

Indeed, there aren't really any candidates who are doing significantly better or worse at this point than their very favorable rating would indicate.

This can be seen perhaps as bad news for those candidates who aren't in the top four currently. None of them have any support bubbling up just beneath the surface that just needs to be harnessed. This includes Minnesota Sen. Amy Klobuchar, who moved up to 6% from 3% in September in the horserace.

If Klobuchar or any other of the non-top four candidates are going to pop in the final two and a half months until the caucuses, they're going to have to convince a lot more caucusgoers to love them.

That may be difficult, but it is possible. Take a look at Buttigieg's numbers. While some of his 16 point jump in the horserace between September and November was merely him catching up to his very favorable rating, part had to do with the fact that his very favorable rating went up by 9 points since September.

Were a candidate like Klobuchar able to have a similar bump in her very favorable ratings, she would be forecasted to jump into the mid-teens in the horserace.

And as for Buttigieg, expect the other candidates to try and take some of the shine off. That could do some damage. Warren's 6 point drop from September to November in the horserace came as she was attacked and lost 8 points off her very favorable rating.

With two and a half months to go, candidates will only get nastier toward those out in front.