State Treasurer Alexi Giannoulias and U.S. Rep. Mark Kirk, the Democratic and Republican candidates for U.S. Senate, are essentially tied, with each garnering 34 percent in support in a new Tribune poll of 600 likely voters across the state. The remaining 22 percent of voters said they were undecided. The poll found African-Americans backing Giannoulias 58 percent to 3 percent, but Kirk lead among collar county and downstate voters.