India's newly-elected Central Bureau of Investigation (CBI) director Ranjit Sinha speaks with the media in December. (SAJJAD HUSSAIN/AFP/Getty Images)

In India’s complex web of coalition politics, it's not uncommon for legislators to use threats, blackmail or rewards to prevent allies from walking away.

On Tuesday, 48 hours after a key ally walked out of Prime Minister Manmohan Singh’s national coalition government, federal investigators raided the home of the regional party politician and searched for an illegally imported car.

Indians have in the past joked that the country’s powerful Central Bureau of Investigation is actually a “Coalition Building Initiative,” suggesting it uses ongoing corruption and criminal investigations against chiefs of regional parties as leverage to help keep things peaceful for the government in New Delhi.

Politicians call the pressures of humoring cantankerous allies ‘Coalition-dharma,’ but it can often lead to coalition drama.

On Thursday, the joke did not seem funny anymore.

Investigators raided 20 site early Thursday, including the home of M.K. Stalin, the powerful local politician from the Dravida Munnetra Kazhagam party, which withdrew its support for Singh’s government. The party had withdrawn the support of its 18 lawmakers earlier this week, leaving Singh’s government shaky. The search was related to a case of alleged tax evasion in the import of foreign luxury cars worth $4 million, officials said.

The media and politicians responded with shock. Opinion swung wildly between allegations of coincidence and conspiracy.

“You all know the sequence of events, this is political vendetta,” Stalin told reporters in the southern city of Chennai. “It is quite clear why I am being targeted.”

Arvind Kejriwal, the intrepid anti-corruption crusader-turned-politician who has long criticized the brazen misuse of the bureau and demanded that it operate independently, jumped in as well.

"CBI raid on Stalin? A day after withdrawal of support? And then govt claims CBI is independent?" Kejriwal tweeted.

The government swung into damage-control mode. Finance Minister Palaniappan Chidambaram said he was not even aware of the raid.

“I strongly disapprove of the CBI action. It is bound to be misunderstood,” Chidambaram told the Press Trust of India.

Said Prime Minister Singh: “We are all upset. The timing of the raid is unfortunate. The government did not do it.”

A CBI statement said the agency went to Stalin’s home not to arrest him but to locate a car, which it did not recover. The bureau said the operation was “strictly in accordance with procedures, and there was no intention whatsoever to target any particular individual.”

But the statement didn't sway public opinion.

Rahul Kanwal, managing editor of the Indian news channel Headlines Today, tweeted, "If CBI is independent & officers did their job, why has entire team been called back & removed from the case. Contradictions galore. Sham!"