DAVIDSON, N.C. (AP) -- As Republicans try to win control of the Senate in the 2014 elections, they may be forced to confront runoffs in key states that could expose conservative-vs.-establishment rifts and allow relatively tiny numbers of voters to pick the nominees.
In North Carolina, Republican Thom Tillis hopes to capture at least 40 percent of the vote on Tuesday's primary to avoid a mid-July runoff. Tillis, the GOP establishment's preferred candidate, would rather focus on Sen. Kay Hagan, among the most targeted Senate Democrats seeking re-election this year.
In Georgia, a large field of Republicans makes a runoff election likely, potentially helping Democrat Michelle Nunn in a state that hasn't elected a Democrat to the Senate since 1996. And in Iowa, the winner of a crowded GOP Senate primary on June 3 will need to capture 35 percent to avoid a state GOP convention, a process that often favors the most conservative candidate.
The outcome of the three Senate campaigns could help determine whether Republicans gain Senate control during President Barack Obama's final two years. They need to pick up six seats for a majority in the 100-member chamber.
Primary runoff elections traditionally draw small turnouts under the best of circumstances. The problem expands in the summer, when many families are on vacation and paying scant attention to politics and other news.
A North Carolina runoff would fall on July 15, and Georgia's would come a week later. Given the timing, "if you had a 15 percent turnout, that would be miraculous," said Marcus Kindley, a former Republican Party chairman for North Carolina's Guilford County, which includes Greensboro.
Results of low-turnout elections are harder to predict. The most motivated voters -- who can include tea partyers and other strongly ideological conservatives -- tend to have proportionately more influence in such elections.
Overtime elections also could play a factor late in the year. A fourth competitive Senate race, featuring Louisiana Democrat Mary Landrieu, holds the potential to stretch into December if she doesn't win 50 percent in the November all-candidates election that includes multiple Republicans. Louisiana's unusual election process provides for a Dec. 6 runoff between the top two November finishers, regardless of party, if no one gets a majority on Nov. 4.
Under one nail-biting scenario, if Republicans have picked up five seats in the November election, a Louisiana runoff could turn into a postelection battle royal for Senate control.
About a dozen Senate races remain competitive, enhancing Republicans' chances of gaining the six seats they need. Party strategists and leaders acknowledge Republicans squandered their chances of winning Senate seats in recent elections, making a goal of 2014 to avoid the self-inflicted wounds that doomed the 2012 campaigns of Todd Akin in Missouri, Richard Mourdock in Indiana and others.
Entering the fall campaigns, Republicans have the advantage of Obama's soft job approval numbers and the challenges that the party in power often faces in the sixth year of a White House administration.
"Primaries or runoffs are only a problem if they produce nominees who can't win the general election," said Brian Walsh, a Republican strategist. "There's a potential for that in one or more seats, but I also get the sense that even among conservative voters there has been buyers' remorse that Republicans have given away" Senate seats in recent elections.
Still, the looming possibility of runoff elections could complicate the outlook for the Republican effort to win control of the Senate.
Tillis, North Carolina's House speaker, has garnered support from establishment Republicans, the NRA and National Right to Life. But it's not clear he has a solid lead over Greg Brannon, a tea party-backed Republican who has the support of Kentucky Sen. Rand Paul, or Mark Harris, a Baptist minister from Charlotte backed by former Arkansas Gov. Mike Huckabee. In all, eight Republicans have filed for the primary.
A runoff could be problematic for Tillis because he would be leading the state House of Representatives during a potentially contentious summer special session that starts in mid-May.
In Georgia, Republicans concede a two-month runoff campaign is likely to follow the seven-candidate May 20 primary.
At the state party's most recent debate, Martha Zoller, a popular conservative talk radio host, warned Republicans that the primary and runoff campaign would yield a nominee who is "battered, bruised and broke."
If the leading contender fails to win 50 percent, the candidate will be forced into a runoff against the second-place finisher.
In Iowa, state Sen. Joni Ernst and businessman Mark Jacobs have led the Republican field, but many voters remain undecided. Republicans view the seat of retiring Democratic Sen. Tom Harkin as a prime pickup opportunity. They criticized Democratic Rep. Bruce Braley, the party's likely Senate nominee, when his comments at a private fundraiser appeared dismissive of farmers.