Illinois Democrat Alexi Giannoulias is getting a boost for his 2010 Senate campaign from the politically potent Service Employees International Union (SEIU).

The SEIU on Thursday endorsed Giannoulias, who is a leading candidate for the seat formerly held by President Barack Obama and currently held by Democrat Roland W. Burris, who isn’t running in the 2010 race.

An SEIU release praised Giannoulias, but it mostly criticized Rep. Mark Steven Kirk, who is the leading Republican candidate for the seat.