Republican presidential candidate Mitt Romney became the first candidate to file for election in Illinois ahead of the March 20 primary.
That also makes him the first to challenge incumbent president Barack Obama in his home state.
Romney filed Monday morning in Sprinfield, Illinois. His filing is time stamped for 8:00 a.m. according to the Illinois Board of Elections Web site.
The junior senator from Illinois endorsed Romney in mid-December.
"I'm making this endorsement because Mitt Romney is a fiscal conservative and a national security hawk," Kirk said. "Those are two values I think are critical for the future of the United States going forward."
Kirk said Romney would do better with the economy than Obama has.
Other Illinois Republicans seem to agree.
Back in October Romney won the in-person voting session of the Illinois Straw Poll with 35 percent.
His closest opponent in the polls, Ron Paul, took first with 52 percent of the poll. Paul's win included heavy online voting.