The model and social media influencer -- who once famously dated Kanye West -- was front and center Monday night in Milwaukee where she was one of the key speakers for night #1 ... and she certainly took a hold of her opportunity and delivered a compelling message.

AR got into the backstory of how she came to support Trump and became a Republican -- and the way she tells it ... it all has to do with her challenging her father, a DT supporter.

Take a listen to the anecdote -- Amber says she came to learn her dad supported Trump and vehemently pushed back on it ... that is, until he challenged her to prove all the things she was saying about the guy, including the notion he's racist/bigoted, etc. ... and she tried.

Amber says she went down the MAGA rabbit hole -- studying Trump rallies and talking to red hat-wearers ... and along the way, she says she realized everything she'd thought she knew about Trump was BS, labeling them as left-wing lies pushed by the mainstream media.

She goes on to say that she eventually came to the epiphany that the MAGA crowd were actually her people ... and Amber further argued life all around was better under DT.

While Amber delivered her remarks -- which were incredibly well-received -- Trump was sitting in the audience looking on, apparently appreciating what he was hearing, smiling wide. When she finally wrapped, he got his feet and gave her a rousing round of applause.

By all accounts ... Amber was effective in her speech, and some have suggested she reached a new target audience that Republicans typically aren't able to connected with.