Chicago area voters on Tuesday choose a Democrat to succeed indicted former Representative Jesse Jackson Jr., in a race that has turned into the first major election clash on gun control since the Connecticut school massacre.
New York Mayor Michael Bloomberg, a champion of tighter gun controls, has poured more than $2 million from his political war chest into the contest in an effort to elect a candidate favoring tighter restrictions.
The Illinois lobbying group aligned with the gun rights group the National Rifle Association, has endorsed a candidate opposed to an assault weapons ban.
The outcome of the special election will be an indication of whether Bloomberg and other advocates of gun control can effectively challenge the money and political influence of the NRA, which has long been a powerful force in elections.
The special election is to fill the seat of Jackson, who resigned last November citing health problems, and pleaded guilty in federal court last week to using campaign funds for personal enrichment.
Jackson was a reliable vote in Congress for gun control. But early polls in the race to succeed him showed that the Democratic primary could be won by Debbie Halvorson, a candidate who has an "A" rating from the NRA and opposes a ban on assault weapons.
Bloomberg elbowed into the race, blanketing Chicago television with ads attacking Halvorson and endorsing Robin Kelly, who supports tighter gun restrictions.
With 14 candidates in the race, the outcome is unpredictable. One public poll published last Friday showed Halvorson holding a slim lead but some private polls have showed Kelly pulling ahead.
The race also is unpredictable because of Chicago's racially charged politics. The district is majority African-American although parts of it stretch south to the predominantly white outer suburbs of Chicago.
Halvorson, who is the only white candidate, has appealed to suburban voters who might be sympathetic to gun ownership. Kelly, who is black, has highlighted a plague of gun violence in Chicago's inner city.
The winner of the Democratic primary is likely to be elected to the seat because the district is overwhelmingly Democratic.