Pete Buttigieg seemed to lose at least one supporter during this week's caucusing in Iowa, and it's all because the woman found he was gay AFTER she cast her vote.

Check out this video from Monday night when a caucus-goer from the city of Cresco in Howard County learns Mayor Pete is, in fact, married to a man ... which came as news to her after she'd already cast her ballot for him. She asks if she can take her vote back.

The Buttigieg precinct captain, Nikki Heever, tells her she's not sure if they can do that ... and then engages in an illuminating convo with the lady about religion and homophobia.

Heever tries to explain it shouldn't matter who a person is married to -- all that should matter in this context is what they believe in and stand for ... but this voter wasn't having it. She insisted the Bible preaches against homosexuality and stuck to her guns.

It's unclear if the woman was able to change her vote in the end, but it's pretty crazy to see that her way of thinking is alive and well ... and can literally be THE difference-maker.

We're on our way to New Hampshire, on to the nomination, and on to chart a bold new course for our country. But only if you're with me.



If you can, please chip in: https://t.co/FkVn86Wbdu pic.twitter.com/RCHF3IbrxO — Pete Buttigieg (@PeteButtigieg) February 4, 2020 @PeteButtigieg