MSNBC's Steve Kornacki says Biden enters his convention with a solid lead. CNN's Chris Cuomo isn't buying it.

The Democratic National Convention may be very unusual this year, but as with other "modern conventions, we have got a whole bunch of polls just as this convention gets underway," MSNBC's Steve Kornacki said Monday night. A CNN/SSRS poll showing Democrat Joe Biden with just a 4 percentage point lead "got the most attention today," but it "looks like the outlier" among the five big recent polls, he said, and "the average of these most recent polls is Joe Biden with an 8-point advantage over Donald Trump."

"Put that in some perspective: Of all the challengers who've run against an incumbent president, this is the best a challenger against an incumbent has been doing at this point since Bill Clinton in '92 against George Bush Sr.," Kornacki said. "Of course, that was the last challenger to unseat a president."

Rachel Maddow asked Kornacki what he says to people who point to 2016 and argue polls mean nothing. He said he gets the critique, but "on her absolute best day, Hillary Clinton could get polls like this, but more often you found that Clinton lead over Trump shrinking to 5, 4, 3 points," while Biden's lead has stayed in the high single digits or low double digits for months. "I keep saying, follow the polling average," Kornacki said. "If the polling average gets down to 5, to 4, to 3 points, to somewhere in that range, then I think you start talking about Electoral College, you start talking about Trump with that pathway he found in 2016."

At CNN, poll watcher Harry Enten agreed that the polling average put Biden in a much better spot than Clinton in 2016, but "there has been some slight tightening over the last month," and Biden is up by much less in the crucial swing states. "It took you 55 seconds, but you finally got to the only point of substance that you've made thus far," host Chris Cuomo needled. "It's all about the Electoral College, it's all about the swing states." The five top swing states are why "the race nationally, in my mind, is actually closer to say a 6-point margin," Enten said, so "I do think this race is closer than folks think it might be just based upon the national polls." Cuomo reiterated his view that "Democrats should be nervous," meeting some resistance from Enten and fellow host Don Lemon. Watch below. Peter Weber