<----- Election Judge. (Head Judge at my poling places.)
If there is a measure on the ballot that even remotely touches on the subject of a shirt the person is wearing, we will ask them to leave. There is no electioneering allowed within 100 ft of the polling place here in Illinois. If all you have are "political" shirts, then wear a jacket over it.
"No electioneering" means just that. Whether we agree with the sentiment or not.
You can express your 1st Amendment rights all you want starting at 101ft from the polling place. The polling place is neutral ground.
And yes, I have had to tell people to leave because of what they are wearing. Even had one lady report me to election comission because I asked someone who was wearing an Obama shirt last election to leave or put on a coat. Got to talk to two investigators from the Secretary of States office because I was "suppressing the vote".
The really fun ones are the ones that stand outside and try to shove flyers and the like in voters hands. I get lots of complaints from the voters, but I tell them as long as they are beyond the "No Electioneering" signs, there's nothing I can do about it. Sorry.