MANDSAUR, India—Wherever India’s farmers are struggling—as they are in this rural community—Indian politicians are never far behind promising help. These days farmers are questioning just how helpful those politicians have really been.

Last year, the farmers traveled to cities big and small to drive home their dissatisfaction, holding large demonstrations and protests. This year, when Prime Minister Narendra Modi and his Bharatiya Janata Party face the electorate in a general election that must be held by May, the farmers...