A special primary campaign for the U.S. House seat vacated by Democrat Rahm Emanuel concluded Monday evening, as voters in Illinois’ 5th District — most of whom are Democrats — choose the candidates for the April 7 general election.

Polls closed at 7 p.m., which is 8 p.m. Eastern time.

The district, which sweeps across Chicago’s North Side and encompasses some near-in Cook County suburbs, is a Democratic Party stronghold. The winner of the Democratic Party’s 12-candidate primary almost certainly will emerge as the strong front-runner to fill the seat.

Emanuel, who resigned in January to become White House chief of staff, won his final House election with 74 percent of the vote. Barack Obama , the former Illinois senator and fellow Chicagoan who appointed Emanuel to his current position, took 73 percent of the 5th District’s presidential vote.

There are competitive contests for two other parties’ nominations, however, with five contenders seeking the Republican nod and six candidates on the Green Party’s ballot.

As is commonly the case for special elections, the biggest factor in the primary outcome is likely to be how many voters trouble themselves to participate in the midst of a Chicago winter.

Out of close to 300,550 registered voters in the district, only about 4,400 took advantage of early voting procedures in the past couple of weeks.

“I would love to be wrong. I would love to have lots of people turn out. But I expect it’ll be fairly small,” Cook County Clerk David Orr told Chicago Public Radio on Monday.

That means the Democratic winner could come from among the elected officials running in the primary who have been able to build upon their already existing name ID with well-funded media campaigns. State Rep. Sara Feigenholtz leads the field with more than $800,000 in receipts as of Monday, followed by fellow state Rep. John Fritchey, who had close to $605,800.

Newspaper endorsements rarely win races for candidates but could make a difference in a race this crowded. Cook County Commissioner Mike Quigley was endorsed by both of Chicago’s major newspapers, the Tribune and the Sun-Times.

If a strong and longstanding base in local politics is a major factor, then the winner could be 40th Ward Alderman Pat O’Connor, an ally of Chicago Mayor Richard M. Daley, who has support from friends in his home base and colleagues on the city council. A strong pull from an ethnic constituency in the highly diverse 5th District could boost a candidate such as [@url@Victor Forys@ http://victorforus.com/], a doctor who, like many district residents, is a Polish immigrant.

And two “outsider” candidates, University of Chicago economics professor Charlie Wheelan and labor rights lawyer Tom Geoghegan, have made also impressive strides throughout the campaign and are widely considered the leading “second tier” candidates.

The Republican primary, meanwhile, has been competitive but relatively fraternal. The five Republican primary contenders plan to spend at least a portion of election night together at a local restaurant to show solidarity, said Mike Wyszynski, campaign manager for candidate Greg Bedell.