Longtime Rep. Tom Latham’s unexpected retirement has induced turmoil in the Hawkeye State, as both parties scramble to find top candidates to succeed the 10-term Republican.

But operatives from both parties have lamented the thin roster of top House hopefuls with a broad appeal in the competitive district. President Barack Obama carried the 3rd District — the state’s most competitive House territory — by 4 points in 2012.

“This isn’t a slam-dunk district for Republicans,” said former Iowa Republican Party Chairman Matt Strawn. “It’s important that we nominate a candidate who can win in November.”

Democrats backed former state Sen. Staci Appel this summer, when she announced a bid to challenge Latham, but now party operatives emphasize the field is open for other Democrats to join. Meanwhile, Republicans have privately expressed concern about two announced candidates, four other likely GOP contenders and the crowded field that could result.

David Young, former chief of staff to GOP Sen. Charles E. Grassley, announced last week that he was moving from the Senate race to run in the 3rd District. Nutrition store owner Joe Grandanette had also announced a primary challenge to Latham before the lawmaker announced his retirement.

Republicans say state Sen. Brad Zaun, who lost to former Rep. Leonard Boswell, D-Iowa, in 2010, is considering a bid. Zaun would likely have strong financial footing in the race, but personal issues — such as a report of a domestic dispute with an ex-girlfriend in 2001 — could hurt him in a general election. Charges were never filed from the incident, according to the Des Moines Register.

Iowa Secretary of State Matt Schultz is also close to entering the GOP primary and could announce his campaign as soon as this week, according to a source close to his campaign. But Republican operatives are concerned because Schultz has not proved an adept fundraiser, and his support for a voter ID law could hurt him with independents in the general election.

Bridge contractor Robert Cramer is also close to announcing a bid for the GOP nomination. Operatives said Cramer, too, could present problems for the party because of his ties to one of the state’s most prominent evangelical social conservative activists, Bob Vander Plaats.

Cable television executive David Oman — a former aide to Gov. Terry E. Branstad — is also eyeing a run, operatives said. Republicans say if Oman jumps in, his background could create a marquee House battle between business and the tea party similar to those playing out across the country.

And there’s more bad news for Republicans: A six-candidate field would likely force the GOP to select a nominee through a convention instead of a primary. Iowa Republicans must hold a nominating convention if no candidate receives more than 35 percent of the vote in a primary.

Often, the most conservative activists constitute the voting delegates at these conventions. In 2002, the last time a convention picked a nominee for Congress in Iowa, delegates picked conservative Rep. Steve King.

An ultra-conservative GOP nominee only boosts Democrats’ hopes of stealing the seat in 2014. But that party is also having some candidate woes in this plum open-seat opportunity.

Appel’s candidacy has not wowed some Democrats. While groups such as EMILY’s List tout Appel’s support for abortion rights, other Democrats say that could hurt her in this evenly split district. Still, those same skeptical operatives have accepted that she will likely be the most credible Democrat in the mix.

Democratic operatives say state Sen. Matt McCoy, the other Democrat eyeing a bid, has ethical issues that would likely make him a non-starter in a primary. In 2007, he was indicted on federal extortion charges, although he was later found not guilty.

Appel may not be Democrats’ perfect choice, but party operatives say the prospect of electing the first congresswoman from Iowa excites the base. More importantly for Appel, this will also help open donor pocketbooks. Appel raised $239,000 in the third quarter, her first as a candidate in the contest.

“One of the reasons [she could clear a field] is Staci does have a fair amount of money in the bank, and is going to come out with another strong quarter,” one national Democratic source said.

This race is rated a Tossup by the Rothenberg Political Report/Roll Call.