Joe Biden Maintains Substantial Lead Despite Major Poll Tightening Ahead of Election

Former Vice President Joe Biden's lead over President Donald Trump has declined slightly over the past week, according to University of Southern California Dornsife Election "Daybreak" Poll.

The USC/Dornsife poll is tracking changes in Americans' views throughout the presidential campaign and predicted that Trump would win in 2016, when it was partnered with the Los Angeles Times.

The latest figures from USC/Dornsife show Biden leading Trump by 11.2 percent on October 20. Biden led by almost 13 points in the same poll on October 13 and has been declining every day since.

These numbers indicate the election tightening slightly but still show Biden with a substantial lead on the president.

The USC/Dornsife poll is a significant indicator. The poll has around 6,000 respondents and is updated every day.

In 2016, USC/Dornsife predicted Trump would beat former Secretary of State Hillary Clinton by 3.2 percent. In fact, he lost the popular vote by 2.1 percent.

USC/Dornsife was one of two major polls to correctly predict Trump would in the 3-16 election. The other, the Investor's Business Daily/TechnoMetrica (IBD/TIPP) poll, shows Biden leading by just 2 points up to October 20.

Poll tracker FiveThirtyEight shows Biden 9.9 percent ahead of Trump. This is an improvement on his position just last month. He led the president by 6.9 percent on September 22.

FiveThirtyEight gives USC/Dornsife a B/C rating for polling accuracy, while the Democrat leads Trump in every national poll listed by the site over the past two months.

The RealClearPolitics (RCP) polling average gives Biden a lead of 7.5 points. This is a decline from October 12, when RCP showed Biden leading by more than 10 percent.

While Biden is ahead nationally, the election will be decided in swing states. Trump won the electoral college vote in 2016 by gaining unexpected victories in Michigan, Pennsylvania and Wisconsin, states once considered part of the Democrats' "Blue Wall."

However, polling for all three states now shows Biden with substantial leads that could cost Trump re-election. The former vice president also enjoys slim advantages in states that are not traditionally considered winnable for Democrats.

Biden is up 1 percent in Georgia and 1.1 percent in Iowa, both states Trump won last time. He's also leading by 3.6 percent in the crucial state of Florida. If the president loses Florida, his path to re-election will become much more difficult.