I believe, Sena is losing its vice like grip. Shiv Sena is down but not out as Narayan Rane and others point out. Narayan Rane is supposed to win this by-election in Malvern, its not a big achievement, there is one more by-election in the near future where 3 of his supporters resigned from Shiv Sena. He has to prove his mettle and make sure all 3 wins with big majorities.
But the stronger Narayan Rane becomes, the more problems for Congress not the Sena, Sena has nothing to loose, as after his victory Rane will be very ambitious and will try for ChiefMinisters post in the near future which Vilas rao Deshmukh or any other congress man will oppose. This is the real problem Congress has to face in the near future which Sena can use to the hilt.
So for now, Sena under Uddhav Thackarey has to lie low and try to be intact with appeasing all the disgruntled elements within Sena