The Democratic Senatorial Campaign Committee is set to release its first TV ad in Illinois, where state Treasurer Alexi Giannoulias (D) is locked in a tight race against Rep. Mark Kirk (R) for the seat formerly held by President Barack Obama. The ad will begin airing Monday and is expected to run for at least a week.

The DSCC placed a $250,000 independent expenditure broadcast buy Friday in the Chicago media market, according to a Republican source who tracks Democratic ad buys.

The latest polls show a very close race between Kirk and Giannoulias in what has long been considered a key Senate battleground this cycle. The National Republican Senatorial Committee has yet to spend any IE money on the race, but it has announced plans to move $3.4 million to Kirk in the form of coordinated funds. Unlike independent expenditures, coordinated funds are limited, and $3.4 million is the maximum Senate committees can spend in Illinois this cycle.

The DSCC, which has a policy of not commenting on its ad buy strategy, declined to discuss the independent expenditure as well as whether the committee has or will pledge funds to Giannoulias in the form of coordinated dollars.

The Illinois buy caps off a busy week for DSCC independent expenditures. The committee released new ads in Washington and Pennsylvania and bought air time in Delaware on Thursday in the wake of Republican Christine O’Donnell’s upset primary victory over establishment favorite Rep. Mike Castle.

NRSC spokesman Brian Walsh seized on the contrast in the committee’s dedicated coordinated funds in Illinois to take a shot at Giannoulias, who garnered negative press after the bank his family owns was taken over by federal regulators in April.

“After they saw what happened to Broadway Bank investors and the Bright Start families, is it any wonder that national Democrats don’t seem to trust Alexi Giannoulias with their money?” he said.