As you might expect, though, the effort in Indiana isn’t nearly as robust as it was two years ago. Between them, Organizing for America and the state party have 39 paid staff members on the ground and a growing list of about 1,600 volunteers; that compares with about 200 paid organizers and 7,000 volunteers at the height of the 2008 campaign.

Democratic leaders note that their goal is not to recreate the political tidal wave of 2008, but rather to improve on the usual turnout for a midterm election. By their calculations — and Mr. Obama’s field organizers do a lot of calculating — some 42 percent of first-time voters in a presidential year normally can be counted on to vote again two years later. Raising that number to something like 50 percent in Indiana could do a lot to blunt the effect of an energized Republican base.

“The Democratic intensity level now is pretty much where you’d expect to see it,” says David Plouffe, the architect of Mr. Obama’s 2008 campaign. “The problem for us is that Republican intensity is just off the charts.”