With six days remaining until voting in the 2020 presidential election is complete, President Trump faces a significant hurdle: He needs to win multiple states where, over the past 100 days, he has never led. It’s not just that Trump hasn’t led. It’s that there are a number of states in which Trump’s support has never topped about 45 percent in FiveThirtyEight’s polling averages.

As we’ve noted, Trump benefited in 2016 from undecided voters shifting in his direction. That was possible because there were a lot of undecided voters — both Trump and Hillary Clinton had the support of less than half of voters. This year, such undecided voters are less common, and candidates polling above 50 percent are more common. So in many states, it’s not just that Trump hasn’t accrued enough support, it’s that his ability to get a plurality of the vote depends not on people making up their minds (undecided voters) but on people changing their minds about supporting former vice president Joe Biden.

There are 20 states in which one candidate has consistently had over 55 percent in the FiveThirtyEight average over the final 100 days or in which the other candidate has consistently been under 40 percent. In every other state, the polling average has occasionally or regularly seen both candidates in that 15-point range.

In 27 of them, though, the lowest level of support seen by one candidate over that period is higher than his opponent’s highest level of support. Thirteen of them have seen Biden with a consistent lead; 14 have seen a consistent lead for Trump.

The fundamental problem for Trump is that the states where he has had a consistent lead — Alaska, Montana, Utah — generally offer fewer electoral votes than the ones where Biden has consistently led. States where Trump has consistently led have an average of 6.9 electoral votes. States where Biden’s consistently led average 12 electoral votes. Now multiply those values by the number of states, and you see the situation.

Or, if you don’t, let’s be explicit. The states that are solid for Biden offer 182 electoral votes. Those where Biden has always led — call them the ceiling states — offer another 152. That’s 334 electoral votes alone, more than the 270 needed to win.

In the states where Trump has consistently led, Biden’s average peak is 43 percent, 7.2 points lower than Trump’s average low. In states where Biden has consistently led, Trump’s average peak is 44 percent, 5.2 points lower than Biden’s average low.

Right now, Trump leads in two of the other four states but, luckily for him, they’re the two states with the most electoral votes. If we assume those margins hold, Trump’s total hits 182 electoral votes.

That, of course, is still nearly 90 votes shy of a win.

In other words, in order to win, Trump needs to win some of those states where he hasn’t led at any point in the last 100 days. In general, this is not as hard as it sounds. In Florida and North Carolina, for example, he has consistently run close to Biden, with his peaks only a point or less below Biden’s lows. Flip those, and he swings 44 of Biden’s 152 votes into his column.

But that still leaves Trump 44 electoral votes shy of victory. The next three states where he has run closest to Biden over the past 100 days are ones in which he has never been above 46 percent in the polling average and includes one, Pennsylvania, where Biden has never been below 49 percent. The closer he gets to 270, the harder it gets for Trump to snag the votes.

In 2016, Trump beat the polls to win the presidency. He could again. But he was also running against a candidate who was hitting her own ceilings in the polls. As we’ve repeatedly pointed out: No matter how much Trump wishes he could simply rerun the 2016 playbook, this election is not 2016.