It's a harsh political reality that has put DMK Chief M Karunanidhi in a bind. As his pet minister A Raja is under fire with the CBI raiding his Ministry over a Rs 22,000 crore spectrum scam, the Tamil Nadu chief minister is reported to have expressed his displeasure to the Congress high command.

But taking on the Centre could snowball into a confrontation between the two allies and impact their ties not just in Delhi but also in Tamil Nadu.

The party's official line is that Raja had in 2007 kept the Prime Minister in the loop over the grant of 2G spectrum. And that by campaigning for him in the elections and bringing him back to the same ministry, the Congress has all along backed Raja.

"The minister has already clarified his stand. Whatever he has said is the party's stand," said DMK Rajya Sabha MP Kanimozhi Karunanidhi.

In a letter to the Prime Minister in December 2007, Raja had defended his first-come-first-served policy in granting spectrum licences, which said, "My intention is to give lower tariff to consumers."

The DMK is adopting a two-pronged strategy. It has decided to tone down its attack on the Centre over the Mullaiperiyar Dam issue, and to rally around Raja.

Raja's party boss Karunanidhi has always had a soft spot for him because he is a Dalit and is close to his family members. Of course, the Opposition says Raja is the party's golden goose.

In its second innings the UPA does not depend on its Tamil Nadu ally's support. It's the DMK that is in power in the state with the Congress strength - a political compulsion that has pushed Karunanidhi on the backfoot.