It's the largest election in the country's history, but many at the consulate in San Francisco were turned away after locations closed at 5 p.m.
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The National Institute of Elections says it was allotted 1,500 ballots but did not have time to register everyone who was lined up outside.
The line spanned for blocks around the Consulate General of Mexico on Sunday.
Mexican voters showed up big time at the San Francisco polls.
"This is a party for democracy in Mexico. We are all very excited and proud that everybody showed up and everybody wants a change, and we're here for that," said Marisa Garcia from San Francisco.
Voters arrived from across the Bay Area, waiting for hours - some saying more than seven.
"Been in the line for probably two or three hours already, and we're halfway there. A lot of people came at three in the morning and they barely left just right now," said Adilene Gonzales from Livermore.
This is the first year Mexican citizens living in the U.S. have been able to vote at the country's consulates. Previously the options were to vote by mail or electronically.
"We've been waiting for five hours," said Pilar Martin Del Camp from San Francisco.
Tara Campbell: "Did you expect this?"
Pilar Martin Del Camp: "Not five hours, but I did expect three. And we're going to be here for like seven. I mean, it's our rights and our obligation towards our country. But seven hours is very patriotic."
And while there was some frustration with the wait, the majority were feeling hopeful for their homeland.
"I'm not surprised, because we all know the stakes are high. This is a historic election. It's a long line, but I'm quite happy to be here and see the turn out of the people," said Varenka Ruiz from Marin County.
The stakes were high, indeed, with both presidential front-runners being women.
"Well, it's a big thing as a woman, you know, coming in. It's a really big thing for me," Gonzales said.
"Women [are] less protected in Mexico. The types of issues we have for women in Mexico [are] pretty high, so to have a woman president who supports single mothers, and the youth, and elders is very important to us," Ruiz said.
"I think I'm going to cry whenever I'm going to vote for a woman. It's huge for Mexico culturally. It's going to be a big role model for women everywhere," Garcia said.