Of course not. Only Republicans are expected to resign under such circumstances. Democrats, on the other hand, are permitted to "stay in the fight." I'm sure we'll hear a lot in the days to come about Kennedy's "heroic efforts to stay in the fight, despite his very difficult personal challenges."
Heard it this morning on ABC Radio News.
You're right--the press wouldn't have asked a Republican if he was going to resign, they would have asked why he hasn't resigned yet.