Particularly since not every poll asks every question or about every candidate. If we want to track the favorability of, say, Ohio Gov. John Kasich over time, it's tricky to find enough poll data to be particularly useful. (Part of this is his fault: He jumped into the campaign very late, with the goal of riding his announcement bump into the debate.) (Which worked.) Other people are left off of polls because asking about the favorability of 17 candidates -- only, say, four of whom anyone has ever heard of -- gets a bit tedious. But it's worth tracking.
After all, you've probably seen this graph, which is the Real Clear Politics polling average over time. The dark red line on there is Donald Trump, who wasn't even included in the RCP average at the beginning of May, leapfrogging everyone with great relish.
That's interesting. But what's more interesting is what's happened to his image. We pulled a series of recent polls back to May (listed at the bottom of this post) to see how each of the 10 main debate participants' net favorability -- those who view them favorably minus those who view them negatively -- has shifted in the past few months.
And without further ado, this is Donald Trump's staggering chart.
He's still not viewed as favorably as many of the other candidates, mind you. He has a fervent core of support which has grown and pulled up his favorability -- and with it, his overall favorability.
But no one else looks like that. Nearly everyone else, shown below, has stayed relatively flat both among Republican voters and all voters.
Here's Jeb Bush, for example -- one of the other candidates who most people have an opinion about.
A slight uptick with Republicans; a slightly larger one with the general population -- but keeping in mind margins of error and how few polls we're looking at, nothing particularly shocking.
And his is one of the better ones. Ben Carson and Marco Rubio are viewed pretty positively and have been consistently.
Mike Huckabee's previously quite-high favorability with Republicans has dipped.
Chris Christie continues to do particularly poorly with Republicans.
Scott Walker is above water with all voters.
Ted Cruz and Rand Paul look pretty similar.
In theory, he has room to grow; after all, he's still viewed pretty poorly. But it raises the big question that's been hanging over his campaign, particularly with that first debate looming: Can Donald Trump expand his base even more? Has he maxed out? The amount of rehabilitation he's done is massive. Is it all he can do?
This is why we need more polls.
Republican voter polls: Gallup, CBS, Marist, Quinnipiac, Quinnipiac, Monmouth, Post/ABC.
All voter polls: Gallup, CBS, CNN/ORC, Quinnipiac, AP, Quinnipiac, Post/ABC.