Update: Coverage of second Republican debate.
Is it time to start taking Donald Trump seriously? Charts like this one showing him with a large and apparently growing lead in the polls seem to say so, but I don't believe it:
Why? Well, the issue is that Trump benefits at the moment from running against a gigantic field of Republican contenders. There's only one Donald Trump in the race, while there are many genuine Republican Party politicians. So many, in fact, that veteran former governors of Texas and New York can't so much as work their way onto a 10-candidate debate stage.
Aggregate them all together, though, and you can see that "real politicians" are kicking Trump's butt:
Of course, if a nationwide first-past-the-post primary election were being held tomorrow, this would be irrelevant. Trump is polling ahead of any of the real politicians, and he would win. But there is no nationwide first-past-the-post primary, and the voting in Iowa and New Hampshire won't start for months. Between today and the settlement of the nomination, lots of these candidates are going to drop out — Bush and Walker and Rubio and Kasich and Christie and Jindal and Huckabee and everyone else have their differences, but none of them wants to see the GOP nominate a fatally weak general election candidate who'll lose to Hillary Clinton and endanger the party's grip on the US Congress.
As candidates start dropping out and endorsing someone left standing, the polls will start looking less like the first chart and more like the second chart.
This isn't to say that Trump isn't worth paying attention to. His level of support seems broadly similar to what Bernie Sanders is pulling down. There's something interesting and important about the fact that a significant minority of Democrats are drawn toward a vision of a Nordic-style Social Democratic Party. And there's something equally interesting and important about the fact that a significant minority of Republicans are drawn toward a vision that broadly resembles France's quasi-fascist National Front.
But Trump is no more going to actually win the nomination than Sanders is.
The difference is that Sanders is facing a party establishment that's already unified around a clear champion, while Republicans have a deep bench of plausible and quasi-plausible nominees. In a weird way, the strength of the GOP field — as reflected in the large number of people with the basic résumé attributes of a presidential nominee — has made the party look more vulnerable to a fringe candidate than it really is.