Manmohan Singh on Friday confirmed long-running speculation that he will not seek a third term as India's prime minister after elections due in May. The move shifts the focus to Rahul Gandhi, who will now lead the Congress Party into the polling—and potentially into defeat if he doesn't start offering some serious ideas.

When Mr. Singh came to office nine years ago, he was hailed as an economic reformer on the strength of his record as finance minister during the "big bang" liberalization of 1991. But he suffered for being more a technocrat than a politician. He lacked both the skills to build an electoral consensus behind bold reforms and the mandate such a consensus would have conferred.

Indian Prime Minister Manmohan Singh and Rahul Gandhi Reuters

Politicians and voters alike knew that real power resided with Congress Party President Sonia Gandhi, Rahul's mother. Mr. Singh's tenure has been dominated by Mrs. Gandhi's agenda, including a dramatic expansion of a welfare state India can't afford and near-stasis or outright backsliding on most liberalization. The past nine years also have been marred by corruption scandals. Little wonder that despite a brief spurt propelled by broader global growth, the rate of economic growth has slowed and the middle class has become ever more exasperated with New Delhi.

Mr. Gandhi already is the Congress Party's vice-president, and despite a lackluster stump speech he at least makes a better show of drumming up broad support than Mr. Singh did. Both factors might allow him to rule with more authority than Mr. Singh wielded if he wins in May.

Yet Mr. Gandhi remains a cipher. He bears a powerful name as the scion of the Nehru-Gandhi clan whose great-grandfather, grandmother and father have all been prime ministers. But to the extent he has articulated any platform at all, it resembles his mother's preference for rural populism over pro-growth reform.

And beyond the economy, he likely would perpetuate the drift that characterizes New Delhi's political class. Mr. Singh reorganized some security services after the 2008 Mumbai hotel attack but otherwise has been listless in confronting violent Islamism at home and abroad. Mr. Gandhi gives little indication of being any different, and he has taken rhetorical swipes at Israel to pander to Muslim voters.

Frustration with the Congress Party helps explain why Narendra Modi of the opposition Bharatiya Janata Party is shaping up to be the candidate to beat. Mr. Modi is campaigning on a record of economic success and effective governance in his home state of Gujarat. Yet his Hindu nationalist background may make him too unpalatable to too many national voters and it's not clear he'd have the chops to scale up his Gujarat successes.

Now Mr. Gandhi has to decide whether he'll offer voters a real reform choice, or whether he'll fall back on promises of handouts and appeals to nostalgia for his forebears. India can ill afford more of the same, and as voters grow more demanding perhaps neither can Mr. Gandhi.