U.S. Rep, Mark Kirk, the Republican nominee for U.S. Senate, holds a six point lead over Democratic rival Alexi Giannoulias, according to the latest poll by Rasmussen Reports.

In a poll taken after Tuesday's primary, Rasmussen said Kirk leads 46 percent to 40 percent. The poll shows that 10 percent are undecided and four percent prefer another candidate. That lead gibes with a poll Kirk touted at the GOP Unity Breakfast on Wednesday that showed Kirk held a modest lead over the current state treasurer.

Among voters not affiliated with either of the major parties, the Republican holds a sizable 59 percent to 22 percent lead, Rasmussen said.

In December, Giannoulias was up by three points over Kirk. In October, the two men were tied at 41 percent each. In mid-August, Kirk held a modest 41 percent to 38 percent lead over Giannoulias.