Sen. Mark KirkMark KirkNBA pulls All-Star Game from NC over bathroom law GOP groups scale back support for Sen. Johnson Top GOP senator: Trump will have little effect on Senate races MORE (R) says he plans to avoid a "partisan jihad" with fellow Illinois senator Dick DurbinDick DurbinSyria activists cheer Kaine pick Democratic National Convention event calendar Opioid package clears key Senate hurdle MORE (D) in this year's midterm elections.
Asked whether he would campaign for Durbin's GOP opponent, Jim Oberweis, ahead of the November midterms, Kirk said he wants to protect his relationship with Durbin.
Oberweis, a conservative state senator, won the Illinois primary last week with 56 percent of the vote over a more centrist Republican.
Durbin is expected to easily win reelection this year. Kirk is facing his own competitive reelection bid in the 2016 cycle.
Oberweis helped lead the effort to push out former Illinois GOP Chairman Pat Brady last year over his public support for gay marriage. Brady eventually stepped down, citing his wife's health concerns.
Kirk's aides had reportedly lobbied in support of Brady during the controversy. Kirk, who supports gay marriage, thanked Brady for his service when he left office.