Election security updates: Voting hours extended in Pennsylvania county

In what campaign aides are classifying as his "closing message" speech, former President Donald Trump is already setting expectations for his supporters to challenge the results of the election, saying Vice President Kamala Harris only has a 4% chance of winning the race.

"So based on what I'm hearing -- she's at 4%. And so we never want to take anything for granted. But we're really doing well," Trump said during his rally in Pittsburgh, Pennsylvania.

Trump again falsely accused Democrats of cheating in the 2024 election, but added that it's "too big to rig."

“I do believe it is too big to rig. They'll try. And they are trying, you know, though. It's too big to rig. This is a big movement," Trump said.

Doubting the fact that President Joe Biden legitimately won the 2020 Election, Trump said that he has since learned.

"This is that big, powerful, vicious party -- that's a vicious machine. They can take all these bad ideas and win elections." he said.

The comments come as the Trump campaign has 230,000 poll observers along with 500 attorneys in every battleground state.

-ABC News' Soo Rin Kim, Lalee Ibssa and Kelsey Walsh

Vice President Kamala Harris made two stops at residents’ homes in Reading, Pennsylvania, and asked for their votes.

At the first stop, Harris greeted a family and followed them to their door so that she could talk to them.

At the second stop, Harris rang the doorbell and surprised the residents, a couple. She hugged the woman who answered the door.

“You know, it’s the day before the election, and I just wanted to come by and say I hope to earn your vote and wanted to just thank you for just giving us the time for this conversation,” Harris told the couple, before they conversed together briefly on one of her recurring campaign messages: finding common ground.

The woman said that Harris had received her vote already, and that she would be working the polls on Tuesday, while her husband would be voting on Election Day.

-ABC News' Gabriella Abdul-Hakim, Fritz Farrow, Will McDuffie and Oren Oppenheim

Former Democratic presidential candidate Marianne Williamson said she cast her vote for Vice President Kamala Harris while emphasizing that no matter who wins, she will do "whatever I can to further the ideal that ultimately love will win."

"No matter who wins, the result is going to be heartrending to roughly half the country. I feel like I want to put my arms around millions of people and tell them it’s going to be OK. I voted for Kamala," she said, in part, in a statement posted to X.

-ABC News' Brittany Shepherd

The intelligence community is yet again sounding the alarm on a Russian "manufactured and amplified" video claiming election fraud in Arizona -- and warned that the activity from Russia will likely focus on battleground states.

"Since our statement on Friday, the IC has been observing foreign adversaries, particularly Russia, conducting additional influence operations intended to undermine public confidence in the integrity of U.S. elections and stoke divisions among Americans," the FBI, ODNI and CISA said in a statement Monday night.

"The IC expects these activities will intensify through election day and in the coming weeks, and that foreign influence narratives will focus on swing states," officials added in the statement.

Russia, according to the intelligence community, is the “most active threat” in the election.

“Influence actors linked to Russia in particular are manufacturing videos and creating fake articles to undermine the legitimacy of the election, instill fear in voters regarding the election process, and suggest Americans are using violence against each other due to political preferences, judging from information available to the IC,” the statement continued.

"These efforts risk inciting violence, including against election officials. We anticipate Russian actors will release additional manufactured content with these themes through election day and in the days and weeks after polls close," officials said in the statement.

Content with the hallmark of a Russian influence operation includes a video claiming election fraud in Arizona and an article falsely claiming that U.S. officials across swing states plan to orchestrate election fraud using a range of tactics, such as ballot stuffing and cyberattacks.

CISA said to seek out trusted sources of information -- the election officials themselves.

-ABC News' Luke Barr