Rep. Timothy Johnson’s preferred candidate in the race to replace him will announce his campaign Monday, much to the chagrin of many Illinois Republicans — including Sen. Mark Kirk (R-Ill.) — who remain irked about the way the six-term Congressman’s post-primary retirement went down this week.

Jerry Clarke, Johnson’s former chief of staff, will announce his campaign Monday for the 13th district seat. An Iraq War veteran, Clarke currently serves as chief of staff for freshman Rep. Randy Hultgren (R-Ill.).

Several Illinois Republicans, including Rep. John Shimkus, have encouraged former Shimkus aide Rodney Davis to enter the race. Davis is still talking over a potential bid with his family, according to Shimkus’ chief of staff, Craig Roberts, who added that Davis is “leaning toward doing it, and if he does, he’ll have our full support.”

A loner in the delegation, Johnson suddenly announced his retirement Thursday — a few weeks after he won the GOP nomination. His announcement stunned many Republicans who were actively helping him with his re-election in the redrawn and competitive district, which is on Democrats’ target list.

In the wake of the announcement, Illinois Republicans presumed that Clarke and Johnson had planned this move for a few weeks.

“They suspect Johnson did this to rig it for Jerry,” one top Illinois Republican said. “A lot of people are furious at the prospect of some kind of back-room deal because this is the kind of nonsense we’ve been putting up with for years with the Democrats.”

What’s more, Johnson can count a recovering Kirk as one of the many Illinois Republicans who are miffed with the way Johnson handled his retirement. Kirk, 52, suffered a stroke in January and has been recovering in a Chicago-area rehabilitation center.

Kirk attempted to phone Johnson to talk him out of retirement, according to two sources familiar with the call. But the six-term House Republican didn’t call him back before his plans went public.

News broke of Johnson’s retirement Wednesday evening, and the Republican held a press conference Thursday morning to declare his intentions. While tearfully explaining his reason for leaving office at the end of this term, Johnson referenced Kirk’s health, according to the Associated Press.

“At my age, three years can be 50 percent of the rest of your life,” he said.

As a result, Kirk’s supporters are miffed because Johnson used the Senator’s health as part of his rationale for retirement.

“I don’t want his health to be a crutch, and I know Mark wouldn’t either,” said an Illinois Republican with knowledge of Kirk’s call.

A Johnson aide did not return an email or message seeking comment about Kirk.

Over the next several weeks, local officials will initiate the process to pick Johnson’s replacement for the November ballot.

Illinois Republican Party Chairman Pat Brady said each of the district’s 16 GOP county chairmen will vote on the new nominee. Their vote is weighted by the strength of the Republican vote in their respective counties.

The party should have a new nominee by the first week in May, Brady said.