IMAGINE a place run by film stars—vain, power-hungry, paranoid, adored. Imagine they had been in charge not for the duration of a reality television series but for decades in a territory containing 72m people and one of the world’s largest cities. It would be a disaster zone, wouldn’t it? Think again, and welcome to Tamil Nadu, one of India’s great success stories—and a state run by actors. It is the ultimate celebrity experiment.

Tycoons and foreign bosses are infatuated by Gujarat, a hard-charging western state where the trains run on time. Policy wonks admire Bihar, an eastern badland that is getting its act together. But India’s most consistent economic performer is in its deep south (see chart). Tamil Nadu has the third-biggest GDP of any state and has grown faster and richer than most.

It is as industrialised as Gujarat—Hyundai, Ford and Renault, among others, churn out a third of all cars made in India there, while the state’s looms dominate the national textile industry. It is also as socially progressive as famously lefty states like Kerala. Compared with the Indian average, more people can read, fewer babies die, and fewer folk are poor in Tamil Nadu.

Those achievements sit alongside a political scene that makes Brazilian soap-operas look prim. The personality cults seen across India today, which lead some to despair, gripped Tamil Nadu decades ago. Power swings between two parties: the DMK and its offshoot, AIADMK.

They have roots in a hardline secessionist movement in the 1930s that disliked north India, defied high-caste Brahmins and rejected the Hindi language (Tamil is the local tongue). In an election in 1967 Tamil Nadu became the first big state to boot out the dominant Congress Party in favour of local groups.

Time has taken the edge off its politics. Tamil culture is now celebrated more than asserted. Few want to split from India any more. Politicians now give rhetorical support and not guns to fellow Tamils in neighbouring Sri Lanka.

Amateur dramatics

But as it has mellowed, the Tamil political scene has got seedier and sillier. Most bigwigs are ex-luvvies of some kind (see article). Parties are little more than fan clubs. The props of office include theatrical arrests of opponents, censorship, defamation suits and giveaways to voters. The chief minister, now in her fourth term, is a Brahmin starlet turned autocrat called Jayaram Jayalalitha, leader of the AIA-DMK party. She has faced several corruption investigations—all unjustified, she insists. “In India the party needs a charismatic leader,” argues Cho Ramaswamy, a confidant who says he both seduced and murdered her on stage in his acting days.

Those looking for a mainstream alternative will struggle. The opposition DMK is run by an 89-year-old playwright and four-times chief minister, M. Karunanidhi, and his son, Stalin. A former DMK minister in the central government is being prosecuted for a telecoms licensing scam in 2008.

“Tamil Nadu is the first state in India that has decoupled politics from economic progress,” declares a big Indian business figure. Like many he argues that the state’s economic success is down to two factors. First, good genes. Tamils have traded across Asia for centuries. The state capital, Chennai, then called Madras, was a hub for assembling tanks and artillery during the second world war, giving it an industrial edge, says S. Muthiah, a historian. A knack for administration dates back to colonial times, when Madras ran south India. Brainy Tamil Brahmins no longer dominate the bureaucracy—they are more likely to be in Silicon Valley. But the civil service still works, say businessmen. It is probably why the public finances look passable.

Second, when they weren’t checking their hair, the politicians did some good in the 1970s and 1980s. Free school lunches raised enrolments. Affirmative action in state-run higher education broke down caste hierarchies and inadvertently “created a new ecosystem of private colleges and universities,” says Lakshmi Narayanan of Cognizant, one of the many IT firms that like the state for its education. The work ethic, loyalty and trust many firms say they find in Tamil Nadu owes something to policies from decades ago that spread the benefits of growth.

Some hope that all this has given Tamil Nadu a self-sustaining momentum and that its politics are but a side show, as relevant to progress as Broadway is to Wall Street. But decades of eccentric governance are catching up with Tamil Nadu.

Graft is endemic. Infrastructure, with its long-term benefits, has been neglected—the state has been spending about 5% of GDP a year on it compared with 7-8% in India as a whole. Carmakers must truck new vehicles through Chennai at night to get to its cramped port. A new airport terminal is opening, a metro is being built and new ports are being readied. But this is all a little late. Most worryingly, electricity supply is 20-30% less than peak demand. Small firms without political clout suffer most.

Political neglect is hurting the economy. Tamil Nadu’s share of manufacturing investment has dropped. GDP growth slowed to 4.6% in the year to March 2013, below the Indian average. Ms Jayalalitha has launched a furious campaign to build power stations and attract investment.

But her eye may also be on a bigger stage: national politics. Tamil parties ally opportunistically with national ones (in March the DMK withdrew from India’s ruling coalition after disagreements over policy on Sri Lanka). Ms Jayalalitha may ally her AIADMK with Narendra Modi, the chief minister of Gujarat, and a likely candidate for prime minister for the opposition Bharatiya Janata Party in the election due by 2014. She may even dream of a leading role herself in a national coalition.

That is unlikely, but it won’t prevent Ms Jayalalitha trumpeting her state as an example to the rest of the country. Tamil Nadu is one of India’s most prosperous places. But it also shows how the neglect of long term problems can catch up with you. Even an actress cannot hide that.