That's what presidential candidate Tulsi Gabbard did in Boston last week -- trading shots with strawweight superstar Weili Zhang ... and TMZ Sports has the video.

Remember, Gabbard played a huge role in helping the Chinese superstar get a visa so she could come to the U.S. on a media tour.

Gabbard, a U.S. military combat vet and current member of the Army National Guard, is a HUGE fan of MMA and has watched Zhang compete for years.

So, when the opportunity came up to spar with the 30-year-old champ, the congresswoman from Hawaii wasted no time strapping on the gear!!

You can see in the video, shot Friday morning, Gabbard knows what she's doing as the two exchange kicks and punches. At one point, famed MMA coach Duke Roufus tells the women, "No elbows!"

After the training sesh, the two hung out and talked -- with Gabbard stressing that sports can help build relationships between countries that aren't exactly on great terms ... like the U.S. and China.

"There is so much conflict, sports like MMA have an opportunity to build relationships and help us get to know each other as people instead of the misunderstanding we see too often."

Zhang tweeted after the meeting, "Today I had the honor to meet and train with Miss @tulsigabbard and she is a very strong martial artist. We had a great training session taught by @coachdukeroufus and his team. It is a happy day when martial arts brings people together."

Zhang is currently is 20-1 as a pro -- on a 20 fight win streak -- and recently called out Valentina Shevchenko, which would be a GREAT fight!