India, Jan. 31 -- In politics, change rarely occurs abruptly. It arrives via a series of seemingly unrelated decisions-an agreement struck overseas, a session halted at home, and a parade intended to reassure. Individually, they appear routine. When read together, they show something more significant: a republic trying how far it can go without strengthening the institutions designed to keep it together.

Recent developments in India point to precisely this moment. The state is growing rapidly-economically, diplomatically, and militarily-while its democratic machinery strains to keep up. The dilemma for India in the coming decade is not whether it can expand or project power, but whether it can do so without undermining the processes that...