Illinois Republicans appeared in disarray Friday over a looming Senate primary with the party's own chairman emerging as a potential challenger to U.S. Rep. Mark Kirk.

Illinois Republican Party Chairman Andy McKenna is "dead serious" about a run for Senate and could potentially enter the race even if Kirk eventually decides to make a primary bid, a source close to McKenna tells the Daily Herald.

McKenna is being prodded to run, in part, by state party donors upset with Kirk's recent vote for a key element of President Barack Obama's agenda, cap-and-trade legislation aimed at reducing global warming, the source said.

That controversial vote - Kirk was one of a handful of Republicans to support the plan - was the focus of an Illinois GOP Congressional delegation meeting Thursday in which both McKenna and Kirk discussed their potential runs for Senate.

A Republican source described the delegation meeting as "cordial," but reports surfaced the lawmakers were turning on Kirk, who has enjoyed the support of the party's infrastructure for months.

That prompted U.S. Rep. Judy Biggert to declared her support Friday for the five-term North suburban congressman.

Meanwhile, the potential for a divisive primary flies in the face of what McKenna has long preached as head of the struggling party.

Since taking the helm in 2005 after his own failed U.S. Senate primary bid, McKenna has advocated for an open-tent philosophy as he hoped GOP contenders could save up their money and image for general election battles with Democrats.

Part of Kirk's appeal for some in the Democratic-led state has been his voting record that sometimes crosses the aisle on environmental and social issues.

Still, national Republicans are anxious about the race as they hope to cut back a 60-vote Democratic majority. And Kirk has appeared increasingly torn about a potential bid as precious time for other candidates to raise money slips away. Petitions are set to be circulated next month.

Kirk said back in April that he would make up his mind in May as he toured the state giving speeches at party functions.

Then on Wednesday, when Democratic Attorney General Lisa Madigan announced she would not seek the seat, Kirk was calling party leaders and informing them he would run, a Republican source told the Daily Herald.

Kirk then told the media he would make an announcement "very soon."

In recently weeks McKenna has stepped into the void, meeting with party leaders in Washington, D.C., leading to Thursday's delegation meeting.

Kirk spokesman Eric Elk declined to comment on McKenna's potential primary bid Friday. But Elk did confirm reports that Kirk and McKenna were in discussions about the race going into the weekend.

The Republican drama unfolded on the same day that incumbent Democratic Sen. Roland Burris announced his would not seek election to the seat he was appointed to by ousted Gov. Rod Blagojevich.