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Trump trails Democrats by a historically large margin

(CNN) First things first: The theme song of the week is Siskel & Ebert & the Movies.

Poll of the week: A new national Quinnipiac University poll finds that former Vice President Joe Biden, Massachusetts Sen. Elizabeth Warren, Vermont Sen. Bernie Sanders, California Sen. Kamala Harris and South Bend, Indiana, Mayor Pete Buttigieg all lead President Donald Trump by significant margins in potential 2020 matchups.

Biden is ahead of Trump by the most (16 points, 54% to 38%), while Buttigeg is up by the least (9 points, 49% to 40%).

What's the point: The Quinnipiac poll was the second probability poll that meets CNN standards and was conducted in August which found Trump down by at least 5 points against all his most likely challengers. In both the Fox News poll out earlier this month and Quinnipiac's latest, he trailed his most likely challenger, Biden, by double-digits. In fact, in an average of all the August polls (those that meet CNN standards and not), Biden was up by a 49% to 39% margin.

We're still over a year away from the 2020 general election, so don't take these polls to the bank.

Still, it's worth pointing out the historically bad position Trump is in. No incumbent president has ever polled this poorly against his likely challengers at this point in the campaign.

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I went all the way back to World War II era in the Roper Center archive to see how presidents were polling at this point against their eventual challengers. I selected the worst poll for the incumbent if there was more than one poll taken in order to give Trump the most generous comparison. In years in which no polls were taken in August the year before the election (i.e. when the last poll for 2020 was conducted), I chose the poll taken closest to this point.

What's clear is the vast majority of incumbents were ahead at this point in the campaign: nine of the 11 were ahead. And for the average incumbent, they led their eventual challenger by 12 points at this point.

Again, Trump trails Biden by 10 points in the average August poll. Trump has not been ahead of Biden in a single national poll taken this entire cycle.

Only two of 11 incumbents in past years, Jimmy Carter in 1979 and Barack Obama in 2011, were behind at this point. They were down by 4 points and 1 point respectively to their eventual challengers (Ronald Reagan and Mitt Romney). Carter went on to lose reelection. Obama went on to win with a small reelection margin -- and there were many polls at this point that had him ahead. (Remember, I'm looking at the worst poll for past incumbents.)

Put another way, Trump's worst poll against any of the top five Democrats at this point is 5 points worse than the worst poll for any incumbent since World War II against his eventual challenger. It's 12 points worse against his most likely challenger, Biden.

As I've already mentioned, we don't know if these polls will hold. What is notable, though, is that Trump is not punching above his approval rating right now. Trump's approval rating has been consistently below his disapproval rating, just like he has been consistently been polling behind Biden. That lines up with what occurred in the 2018 midterms: Republican House candidates got the same share of the votes as Trump's approval rating, 45%.

Trump has time to turn his reelection ship in the right direction. But in the 10 months since the Republicans lost the House in 2018, he's in no better shape. You could even argue he's in a worse position.

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