Gretchen's Take: Unfavorability could be the key to 2016

Donald Trump's continued rise in the polls is obviously good for him, but more importantly, bad for two other candidates in particular -- Jeb Bush and Scott Walker.

Walker's standing in Iowa has almost evaporated. And Bush's favorability has also taken a major hit. Before Trump was a serious candidate his negatives were the highest in the field. but check out what's happening now.

According to this recent CNN-ORC poll, Trump's favorability now stands at 36 percent while Bush's stands at a slightly lower 34 percent.

But often the unfavorablity category is the key to polling. And after the first debate Bush saw his unfavorability rating jump 13 percent from late July to 56 percent from 43 percent.

The last three national polls before the debate all had Jeb Bush second behind Trump but in the two polls released since the big night, Bush has dropped to second in one and fourth in the other. so while likability is important it's sometimes the unfavorable number that can mean more.