Antonio LaMotta, 61, and Joshua Macias, 41, allegedly drove to Philadelphia from Virginia in a Hummer SUV and had two loaded semi-automatic handguns, one semi-automatic AR-15 style rifle and ammunition, the district attorney's office said.
Pennsylvania has become one of a handful of states that could decide the US presidential election following Tuesday's vote. If Democrat Joe Biden can retain a narrow lead in that state over Republican President Donald Trump, it would give him the presidency.
Protesters supporting both candidates have gathered outside the Pennsylvania Convention Center in recent days for what have been largely peaceful demonstrations.
LaMotta and Macias were each charged with carrying a concealed firearm, a felony, and carrying a firearm on public streets or property, a misdemeanor.
Local media reports showed stickers on the suspects' vehicle promoting QAnon, a pro-Trump antisemitic conspiracy theory. The unfounded theory posits that Trump is secretly fighting a global cabal of child-sex predators that includes prominent Democrats, "Hollywood elites" and "deep state" allies.
Facebook and Twitter accounts that appeared to belong to LaMotta show numerous postings related to the conspiracy theory.
"QAnon is a positive military operation that is working to take down the deep state," reads one April Facebook post.
Anita LaMotta, the suspect's mother, told Reuters in a telephone interview that he had traveled to Philadelphia because "he wanted to help" in the event riots broke out.
LaMotta and Macias did not respond to requests for comment. It was not immediately clear whether they have attorneys.Macias billed himself online as a strategic adviser for a grassroots group called Vets for Trump. A group spokesman said Macias was no longer affiliated with them.