But the cybersecurity executive told CNBC's Jim Cramer that he is less certain when it comes to targeted misinformation campaigns that seek to change people's minds — and therefore, the way they vote at the ballot box.
"I'm not worried about the vote count. I'm more worried about those influence operations that you don't even know are happening to you," Mandia said on "Mad Money."
Actors with nefarious intent, such as foreign governments, can hide behind the anonymity of the internet, said Mandia, whose company works with other businesses to investigate and prevent cybersecurity attacks.
The former Air Force officer also pointed to the rise of artificial intelligence and deepfake technology as vehicles to spread misinformation.
"And you don't know if that's an element from another nation just trying to sway the 5% to the right or the 5% to the left," said Mandia, whose company has been hired to work with Facebook and Google to spot online disinformation.
The special counsel's report on Russian interference in the 2016 presidential election found that Russia's Internet Research Agency reached millions of Americans on social media, using false accounts to influence voters and, in some instances, drive them to manufactured rallies.
Many observers are worried that similar online campaigns could target the 2020 election, too.
"But when it comes to hacking the polls, I just don't think that's going to happen," Mandia said.
Even if there are direct attempts to hack voting machines or other elections systems, "whether successful or not, the evidence is going to be there," Mandia said.
"It's not going to be tolerated very well by our government, and I just think all the vendors are coming together with government agencies to safeguard the election," he said. "So I feel pretty confident. We're going to do a lot of work between now and then."
Stopping the spread of misinformation, though, is an entirely different matter, Mandia said.
"That is a tough thing to prevent," he said.