The U.S. is less than a month away from deciding who will become the next president.

Joe Biden leads by over nine points in aggregate national polling data, but Democrats are cautiously optimistic after 2016. Hillary Clinton enjoyed similarly large leads but lost the race to Donald Trump with key defeats in Michigan, Wisconsin and Pennsylvania.

One major difference between the two presidential races is the candidates. Trump is still part of the equation, but he is now the sitting president. There is no longer the intrigue of unknown possibilities for some voters, as they have seen what he has done in three and a half years said Dr. James Riddlesperger, a political science professor.

Joe Biden is also viewed more favorably by voters than Clinton was.

“In 2016 we had the two least popular candidates in United States history,” Riddlesperger said. “It’s not that way this year, most voters tend to see a relatively big contrast between the personality and character of President Trump and the personality and character of Joe Biden.”

This contrast has also decreased the number of undecided voters in the electorate, which played a big role in 2016.

Riddlesperger said about 15% were undecided in 2016, a lot of whom broke towards Trump, compared to only about 7% this year. That means the polling should be a little bit more accurate this year.

Riddlesperger also predicted a rise in voter turnout.

“I think that voting turnout is going to be much more like what it was in 2008. There are even some people thinking it’s going to be a little bit greater than that because mail-in voting is more accessible now than it was, and people seem to be more motivated to vote in general,” said Riddlesperger. 

The increased reliance on mail-in voting has also led to calls from President Trump that voter fraud will be extremely common this year and the election will be “rigged.”

Riddlesperger said there is no evidence that mail-in voting increases voter fraud. He did add that it is hard to estimate whether there would be fraud because it’s impossible to be in someone’s home with them as they fill out their ballot.

“The specter of having somebody calling into question the results of the election is something that is particularly chilling in a democracy,” said Riddlesperger.