Kirk's staff told ABC7 the senator would not be available for an interview Thursday, but Kirk and his hardline cohorts have forced a compromise that could pave the way for the chamber's passage of immigration reform.
It's the far-away (from Illinois) U.S. border with Mexico that concerned Kirk. He and some of the most conservative Republicans demand that before any other reforms happen, it be made more secure.
"To get comprehensive immigration reform right, we've got to first secure the border," said Senator John Hoeven, Republican of North Dakota.
In the compromise amendment, patrol officers along the border would be doubled to 38,000, 700 miles of fencing would be added, with more radar and electronic equipment, all of it costing, by some estimates, tens of billions of dollars.
In a statement, Senator Kirk wrote: "once the Senate adopts our amendment, I will be proud to vote for a bill that secures our border and respects our heritage as an immigrant nation."
Immigration reform advocate Lawrence Benito cannot understand why an Illinois senator wants billions more for border security when Arizona's two Republican senators were satisfied without the additional expense.
"Both senators from the state of Arizona understand the border," said Benito. "If it's good enough for them, it should be good enough for Senator Kirk."
Last week in Chicago, several Latino elected officials said Kirk had a "racial blind spot" and did not respect them or Illinois' sixth-largest-in-the-nation immigrant population.
"Folks are going to remember that Senator Mark Kirk sided with the most conservative tea party loyalists in the senate," said Alderman Ricardo Munoz, an Illinois Democratic Committeeman.
Also on Thursday, Kirk told Chicago Sun Times columnist Lynn Sweet that Chicago was "mainly a Polish immigrant city" and that he was "trying to learn Polish".
A group calling itself the Polish Initiative issued a press release to remind the senator that Poles make up only 7.5 percent of the city's immigrants, while Latinos are nearly 48 percent and Asians comprise 27 percent. There was no explanation Thursday from the senator's office on why he thought the Polish percentage was so high.