Debbie Halvorson chats it up at a farmer's market in Bloomington, Illinois. (Flickr/Gemma Billings)

Chicago—Most countries take special elections to fill vacant seats in their national legislative chambers far more seriously than does the United States.

In Britain, in particular, off-the-clock “by-elections” are recognized as testing grounds not just for candidates and parties but for issues. They are thoroughly covered by the media and often treated as mini-referendums that can send powerful signals regarding hot-button policy debates.

American media outlets and pundits are less inclined toward that sort of analysis. But a crucial Democratic primary to fill a vacant Illinois US House seat is shaping up as test that could well meet the “by-election” standard when it comes to providing an indication of popular sentiment. This race will test the question of whether ties to the National Rifle Association have become politically toxic among Democrats. Of course, it is not the only test, or even the perfect one, as this is an predominantly urban and close-in surburban district. Many of the Democrats who have NRA ties—or who try to walk a middle line with regard to its demands—represent districts and states that are more rural and have strong hunting traditions. But the dynamics in this race, and the moment at which it is playing out, have the potential to send a message of consequence.

Timing is everything when it comes to the question of whether a special election serves as a mini-referendum, as Republicans learned when they lost a historically Republican seat in upstate New York during the 2011 debate over Congressional Budget Committee chairman Paul Ryan’s schemes to assault Social Security, Medicare and Medicaid.

And the timing of this primary contest makes it a big deal, as there are still many Democrats who, even after the horrific Newtown slayings of December and the January killing of Chicago high school student Hadiya Pendleton just days after she performed at President Obama’s second inaugural, seek to play the margins on the gun debate.

Illinois’s 2nd congressional district, which takes in Chicago’s southeast side and the city’s south suburbs, will fill the seat vacated by the resignation of Congressman Jesse Jackson, Jr. The district is overwhelmingly Democratic. A majority of the voters are African-American, as are most of the seventeen candidates competing in the Democratic primary to replace Jackson. But one of the leading contenders, former Congresswoman Debbie Halvorson, is a white Democrat who represented a nearby district before losing to a Tea Party Republican in 2012.

In the 2012 Democratic primary, Halvorson challenged Jackson but won only 29 percent of the vote. At least one January poll suggested she was attracting about the same level of support this year. However, as a former congresswoman running in a crowded Democratic field, she is seen as a serious contender.

This is where the “by-election” measure comes in.

Halvorson has a history of working closely with the National Rifle Association, and received NRA endorsements in her 2008 and 2010 races, winning special praise for her vote to allow concealed weapons in national parks. In this race, Halvorson has tried to distance herself from the NRA, yet she continues to oppose many gun-control proposals, including an assault weapons ban.

One of Halvorson’s opponents, former state representative and current Cook County (Chicago) Chief Administrative Officer Robin Kelly, has done everything in her power to make the election a referendum on the gun issue.

Kelly’s media campaign is all about the issue, which is a critical one in a district that has mourned many of the deaths that have made the Chicago area a focus of debates about how to address America’s staggering rate of firearms deaths.

Help me fight gun violence,” declares Kelly, who is running on “Robin’s Pledge,” a five-point commitment to:

1. Pass a comprehensive ban on assault weapons.

2. Eliminate the gun show loophole.

3. Never receive support from groups that oppose reasonable gun safety legislation.

4. Ban high capacity ammunition magazines.

5. Support laws that prohibit conceal and carry permits.

Kelly is no newcomer to the issue. A decade ago, as a newly elected Illinois legislator, she sponsored legislation to reduce gun violence by banning straw purchases of firearms. It was co-sponsored by then–Illinois State Senator Barack Obama.

Obama, who made the gun issue central to his 2013 State of the Union Address and to a recent visit to Chicago, is not backing anyone in the Illinois special election. But a number of top Democrats, including Illinois Congresswoman Jan Schakowsky and Congressmen Bobby Rush and Danny Davis, have taken the rare step of entering the race to back Kelly. So, too, has New York Mayor Mike Bloomberg’s Independence PAC, which has spent more than $1.3 million on ads that blister Halvorson for her past ties to the NRA and that highlight Kelly’s candidacy. A Kelly win will provide more evidence that Bloomberg's willingness to move money into races around the country, including Democratic primaries, is redefining the gun debate as it plays out in electoral politics.

There are other credible candidates in the race, including Chicago Alderman Anthony Beale. But on Sunday, a top contender who had attracted significant labor backing, State Senator Toi Hutchinson, quit the contest and endorsed Kelly.

“I am simply unwilling to risk playing a role going forward that could result in dividing our community at time when we need unity more than ever,” said Hutchinson, a former aide to Halvorson. “In the wake of horrendous gun related crimes all across our country, I agree with Robin that we need to stand together to fight gun violence, but Debbie Halvorson been wrong headed in her refusal to moderate her views on banning dangerous assault weapons.”

No crowded election contest can ever be a pure referendum on a particular issue, especially in a diverse district that faces many challenges. But if Kelly prevails, the result will send a strong signal regarding the ongoing emotional and political power of the gun issue and the extent to which an NRA tie can become a primary problem for Democrats—and some Republicans—who align with the group.

As Sam Kleiner writes, the NRA has reversed its stance on states’ rights.f