Before giving a go-ahead to CBI raids at the residences of former telecom minister A Raja in connection with the 2G scam, the Congress-led UPA government had "taken into confidence" DMK boss M Karunandihi on the move.
Congress sources said Karunanidhi did not resist the move, an indication to which also came from his statement that action would be taken against Raja if found guilty.
Till now, Karunanidhi has been strongly defending Raja.
"There are serious local compulsions. Tamil Nadu is going to polls early next year. He does not want to carry any baggage to elections," a senior Congress leader said.
UPA troubleshooter and finance minister Pranab Mukherjee has been in regular contact with the DMK chief over the 2G issue that has stalled the proceedings in parliament for 19 consecutive working days.
But the raids are unlikely to cause any strain on the Congress-DMK alliance, as any break in ties would be detrimental for both the parties.
"No doubt, these are testing times for the alliance but both parties need each other," the leader said.
While the Karunanidhi government in Tamil Nadu depends largely on the backing of 34 members of the Congress, the support of the DMK with 18 MPs is vital for the survival of the Congress-led UPA government at the centre.
Officially, the Congress maintained that the action (raids) was a "culmination" of the investigations and asserted its alliance with the DMK was intact.
"We have a political relationship with DMK encompassing the entire spectrum of symbiosis which is between two political establishments. If at all there has been allegations of corruption, no responsible party can object to investigations," Congress spokesman Manish Tewari said.
As of now, the Congress does not want to disturb its more than six-year alliance with the DMK given that it's wary of having any truck with AIADMK leader J Jayalalithaa, who had offered the support of her 9 MPs to the UPA government in case the DMK pulled out on the Raja issue.
She also asked Congress president Sonia Gandhi to forget the past misunderstandings between them. But the Congress has so far resisted the offer. "She is a mercurial personality," a leader said.