I think Rush could use his voice to alert the 20+ million audience members he has, but it would certainly be a slippery slope, as the Democrats will charge he has no right to attack Kerry because he didn't serve in the military. Attacking Kerry's military service is up to guys like Tonk and the Swifties.
Who does not think Hanoi Kerry has a hand in this?
Democrats Demand Bush Halt Attacks on Their Senate Leader
http://www.freerepublic.com/focus/f-news/1340618/posts