The three Senators in question are Lamar Alexander of Tennessee, Pat Roberts of Kansas, and Mike Enzi of Wyoming. If, for the love of this country, you live in one of those three states, it's absolutely imperative you contact your Senator and repeatedly to make sure this happens.
As for those in the rest of the forty-seven states, it wouldn't hurt to contact them, either. They need to put country before party. Don't let them make the trial into a farce.