Rautahat, Feb. 1 -- On a sweltering June afternoon last year, a crowd of supporters gathered to greet chairman of the then CPN (Unified Socialist), Madhav Kumar Nepal, at its party office in Gaur.

The former prime minister, who has won multiple elections from his Rautahat constituency, was the chief guest. While party leaders expressed their views, his cell phone rang continuously. When Nepal finally received the call, it sent ripples through the event and beyond-a corruption case had been filed against him by the country's anti-graft body.

Within hours, the campaign rally dispersed, and he returned to Kathmandu under a cloud of controversy that now looms over his fresh bid for the House of Representatives elections.

The Commission for...