I'm a "supporter" and I know exactly what he means. Means he'll fix all the voting shenanigans so that illegals can't vote and so that democrats can't "rig" and stack the election like last time. See? Not so much a hateful whistle as it is understanding your supporters, what's important to them, and appealing to that with your own words.
Thank you for the actually plausible explanation.
It does not even matter than there was no rigging, no illegals voting, no shenanigans. The truth has never been an effective counter to rhetoric, I get that. But it's an entirely plausible explanation for what a supporter would think.
But after yesterday, maybe we will all agree together than the elections are rigged? ;-). You guys can't put that genie back in the bottle. Everyone thinks it's totally cool until the other side uses it right back.