Obamacare allies aim to expand Medicaid, the low-income government health program, in a handful of states via ballot measures. But they face staunch opposition before Election Day and no guarantee of success after it even if they win over voters.

On Nov. 6, voters in Idaho, Nebraska, and Utah will decide through ballot measures whether to allow more people on the Medicaid program, a move already advanced by 33 states and the District of Columbia. Voters in a fourth state, Montana, will decide whether to make the expansion permanent.