The last-minute candidate scramble is part of Democrats' against-the-odds effort to flip a Republican seat after the GOP-led redrawing of the state's congressional map.
The Senate is set to vote later this week on a three-year extension of Affordable Care Act subsidies that Republicans oppose. The G.O.P. has yet to coalesce around an alternative.
Republicans in Indiana's state House approved a new map that would give the GOP up to two more congressional seats. But the state Senate might not sign off on it.
