Three weeks ago, the primary in the northeastern Indiana district of then-Rep. Mark Souder drew more than 80,000 Republican voters to the polls. But an approaching process of selecting a GOP nominee to replace the recently resigned Congressman will involve fewer than 500 party activists — prompting interested candidates to run very targeted campaigns centered on personal contact.

That group of GOP precinct committeemen will convene a caucus next month, probably on June 12, to choose someone to run in Souder’s stead. Many would-be Republican successors are waging abbreviated campaigns that will more closely resemble a Congressional leadership race or a whip count on a major vote than a traditional primary campaign that relies on fundraising and TV and radio advertisements to reach a broad swath of the electorate.

In a race like this, the universe of voters is known and small, so telephone calls, e-mails and letters will be the media of choice. Personal relationships and professional networking also matter.

“It’s a lot more targeted and a lot more personal,” an Indiana GOP operative said. “In a general election campaign, a candidate can’t call every single voter that’s out there. Something like this is a little more manageable, and you’re going to get through your universe quicker.”

“It’s less driven by media than it is by personal contacts,” said Steve Shine, the chairman of the Republican organization in populous Allen County, which contains Fort Wayne.

Auto dealer Bob Thomas, who is seeking the seat after placing second to Souder in the primary, knows that he will have to run his caucus campaign much differently than the primary, where he spent heavily from his own pockets to air television commercials.

In a caucus campaign, Thomas said, “advertising doesn’t do you any good. Direct mail might work if you send them all some information, letters and things like that. So it’s direct mail and phone calls.”

That a caucus campaign is more manageable and inexpensive than a primary helps explain why so many Republican candidates — 10 or more — have said they are running. So does the distinct conservative tilt of the district, where the GOP nominee will be heavily favored against Democrat Tom Hayhurst, a former Fort Wayne councilman, in both the general election and in a special election that GOP officials now expect will be held on the same November Election Day.

Unlike the primary, the caucus will have a majority-vote requirement and could feature shifting loyalties over multiple ballots.

“In a caucus, anything can happen, whereas a primary is more cut-and-dry — you either are the top vote-getter or you aren’t,” Shine said. “In a caucus, you can be the top person in round one and by round four somebody else could be on top. So the opportunities are more abundant than in a primary.”

One of the leading candidates is state Sen. Marlin Stutzman, who is getting a second chance to serve in Washington after losing the May 4 Senate primary to ex-Sen. Dan Coats. Stutzman’s competitive effort boosted his profile in northeastern Indiana and in some national conservative circles.

Republican sources also identified state Rep. Randy Borror as another leading contender. He has close ties to Gov. Mitch Daniels (R), though the governor is not backing a candidate.

Other Republicans who plan to run include Fort Wayne City Councilwoman Liz Brown, state Rep. Wes Culver and local television anchor Ryan Elijah.

Also in the race are the three Republicans who held Souder to less than a majority of the primary vote: Thomas (34 percent), attorney Phil Troyer (17 percent) and property manager Greg Dickman (2 percent). Thomas is seen as the most viable of the three.

Thomas’ pitch to the precinct committeemen is that he has business experience and isn’t a “career politician,” that he acquired valuable name recognition during the primary and that he took on Souder when almost no one else would.

“I stepped up when it was tough,” Thomas said. “I went ahead and put all the blood, sweat and tears behind challenging an incumbent back three months ago and almost none of these other guys who are in it now, they didn’t have the guts or the tenacity to even try that. So I have the legitimacy of being in this from the beginning.”

Terry Hively, Troyer’s campaign manager, acknowledged the smaller universe of Republican voters in a caucus but noted the very short time frame — less than three weeks — in which to reach them.

“Our target area is smaller,” he said. “It may seem like it would be easier to reach, but when you only have 16 days, you don’t have a lot of time to waste here.”