It's setting up a showdown, as foreign leaders hold off on recognizing the results.
Venezuelans in Chicago are watching closely.
In Venezuela, thousands took to the streets Monday to protest Maduro.
The country's economy has plummeted since he took office 12 years ago, leading to mass immigration.
And that has had a direct impact on Chicago, where over 45,000 mostly Venezuelan migrants have arrived in the last two years.
Sunday, the Illinois Venezuelan Alliance rallied to bring attention to the crucial election.
People lined up for hours across Venezuela to vote.
Many are in support of opposition leader Edmundo Gonzalez, and hoped he would unseat Maduro, who has been in power for 12 years.
They say the outcome could determine if people stay or decide to leave their homeland to come to the United States.
Millions of Venezuelans have left in search of opportunities abroad, and have come to the U.S., which has had a big impact on the migrant crisis.
"Many of them have not been able to find a better life," demonstrator Ana Serafin said. "As a matter of fact, many of them have died trying to find a better life. So today, we really want these elections to happen in the most specific way possible, the most democratic way possible, for us to find the freedom that Venezuela deserves."
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Sunday night, there were several car caravans in the Loop and a huge celebration at Grand and Kedzie avenues, as exit polling showed President Maduro on the verge of losing.
But, that changed in the hours ahead, as Maduro was eventually declared the winner.
"It was devastating for us to believe we lost the election. Clearly the election is stolen," said Ana Gil Garcia, with the Illinois Venezuelan Alliance. "This campaign was about going back. I believe we have many many people ready to go back."
Gonzalez said all election rules were violated, as the opposition questions the voting tallies.
Illinois Sen. Dick Durbin posted on X Sunday night that the regime must respect the people's votes and not steal another election.
Shortly after midnight, the National Electoral Council said Maduro secured 51% of the vote, overcoming the main opposition candidate, González, who garnered 44%.
But the electoral authority, which is controlled by Maduro loyalists, didn't immediately release the tallies from each of the 30,000 polling booths nationwide, hampering the opposition's ability to challenge the results after claiming it had data for only 30% of the ballot boxes.
U.S. officials are calling on Venezuela to make the results public.
"We have serious concerns that the result announced does not reflect the will or the votes of the Venezuelan people," U.S. Secretary of State Anthony Blinken said.
Because the U.S. does not have diplomatic relations with Venezuela, Venezuelans in the U.S. were not able to vote.
But that doesn't mean they aren't using their voices to continue pressing for change.
For now, they are supporting the U.S. government's call for election authorities to publish a detailed tabulation of Sunday's vote.
The Associated Press contributed to this report.