The rest of the field had no trouble saying it.

Elizabeth Warren told the New York Times “without hesitation” that Trump gave white supremacists aid and comfort. “He’s done the wink and a nod,” she said. “He has talked about white supremacists as fine people. He’s done everything he can to stir up racial conflict and hatred in this country.”

Beto O’Rourke told MSNBC Trump made it “very clear” that he’s a white supremacist.

Bernie Sanders told CNN’s Jake Tapper over the weekend that he believes Trump is a white supremacist.

But Biden is reluctant, interestingly:

‘Why are you so hooked on that?,’ he responded to DailyMail.com during his visit to the Iowa State Fair [when asked if Trump is a white supremacist].

‘You just want me to say the words so I sound like everybody else. I’m not everybody else. I’m Joe Biden. I’ve always been who I am. I’m staying that way,’ he added…

‘He is encouraging white supremacy. You can determine what that means,’ he said. ‘I know it’s like everybody wants everybody to call somebody a liar. I don’t call people liars. I said they don’t tell the truth. Okay? You want to hear me say liars so you can put out that Biden called someone a liar. That’s not who I am. You got the wrong guy.’

What’s the difference between “Trump is a white supremacist,” which is no-go for Joe, and “Trump encourages white supremacy,” which is fine? Dave Weigel thinks it’s a function of Biden’s respect for institutions. Just like how he’s more likely to refer to Trump as “Mr. President” than the rest of the field is, he’s more reluctant to call the president of the United States a white supremacist. Noah Rothman believes it’s a subtle bit of strategy aimed at Trump’s voters: “Telling voters they backed an overt white supremacist makes them culpable, defensive. The latter gives them plausible deniability.” If you’re Joe Biden and your strategy depends upon picking off some of Trump’s working-class white support, you need to be careful about accusing them of having voted for a racist in 2016. That might come off a bit too much like Hillary’s “deplorables” comment. Focusing on Trump’s actions as president (“encouraging white supremacy”) creates some distance from that accusation. Trump voters can’t be blamed for not foreseeing how Trump might misuse the bully pulpit as president, or so Biden means to imply.

Jeryl Bier points to this distinction drawn a few days ago by Alexandria Ocasio-Cortez:

Trump fans haven’t been infected with “the virus,” Biden is suggesting, even if their hero is helping to propagate it. Emphasizing Trump’s actions (“encouraging white supremacy”) instead of branding his beliefs (“white supremacist”) also makes it harder for Trump to dodge the accusation, notes Benjy Sarlin. He can flatly deny what’s in his heart, but if you’re pointing to a specific tweet, like the “go back where you came from” knock on Ilhan Omar, he has to defend it on the merits.

Biden said this at an event in Iowa, incidentally, where Monmouth has been polling this week. Result:

Grandpa Joe is steady. Warren is on the rise. Bernie, who finished just a whisker behind Hillary in Iowa in 2016, is vanishing from the race. (As is Beto O’Rourke, who dropped from six percent there in April to … <1 percent now.) An interesting question: If Sanders were to drop out, who would benefit most? My hunch is Warren because they’re progressive peas in pods, but friends on Twitter reminded me today that it’s actually Biden who’s the second choice of a plurality of Bernie voters in various polls, as they overlap in appealing mainly to older white working-class voters. Would Biden still be their second choice over Warren if Bernie endorsed her, though? We’ll probably get to find out.

One more number. Note the trend:

Democrats are leaning more heavily towards electability in a nominee as the race progresses, which is good news for Biden. And not just in Iowa.

Here he is today elaborating on how Trump “encourages” white supremacy. Exit quotation from Grandpa Joe: “We choose truth over facts!” Er, what?