Joe Jonas -- Campaign Endorsement Leads to High School Presidency [VIDEO]

Joe Jonas wields great political power ... among high schoolers at least ... after his campaign endorsement helped a girl win her student council's presidency.

Here's how it went down ... the JoBro was at Monday night's Los Angeles Kings game when he was approached by a fan for a photo. She then took it a step further ... and asked him to film a short video telling the students of Culver City High School to vote for her for student council president.

He did and Mia posted the vid to her Instagram page that night ... and won the election Wednesday morning. Mia (middle) tells TMZ she doesn't think she won the election JUST because of the video, but she did have a few people in the halls at school tell her they voted for her because of it.

Joe tells TMZ, "Really excited the ad worked! I've actually launched a political ad firm - but only for high school and college campaigns, and only while I'm at sporting events. We're open for business!"