The Chicago Sun-Times reporter who co-wrote a story on how Illinois Republican gubernatorial candidate Bruce Rauner (R) allegedly threatened a business associate and then was reportedly targeted by the Rauner (pictured) campaign announced his resignation from the newspaper on Tuesday.

The reporter, Springfield, Illinois bureau chief Dave McKinney, wrote a long letter about how after he co-wrote the story he was put on leave by the Sun-Times. He also described how, when he came back to the paper, he was “advised” not to have his byline on reporting related to the company that Rauner and his business associate argued over.

He noted that he was pulled off his beat and his reporting for that day was “removed inexplicably from the Sun-Times website.”

McKinney, in his letter, did note that top members of the Sun-Times defended him against criticism from the Rauner campaign. McKinney also noted that the Sun-Times recently broke a three year no-endorsement policy and backed Rauner. McKinney suggested that there had been a “breach” in the wall between the owners of the paper and the newsroom. He concluded the letter saying that under the circumstances he had to resign.

He wrote, “I’m convinced this newspaper no longer has the backs of reporters like me.”

“We reporters have a healthy suspicion of both parties and candidates,” McKinney wrote. “It’s our job. It’s regrettable that this issue has emerged in the homestretch of an important election in Illinois, but respectfully, this isn’t about either candidate or the election. It’s about readers and their trust in us. So my decision could not wait. I hate to leave, but I must.”

“And so, it is with great sadness today that I tender my immediate resignation from the Sun-Times.”

In response, the Rauner campaign said the Sun-Times decision to post the story was “irresponsible” according to CBS’s Chicago affiliate. Trover also said that McKinney had “an extraordinary conflict of interest” given that he is married to Democratic political operative Ann Liston.

Read McKinney’s full letter, posted to his wordpress blog, here.

Rauner is the Republican candidate trying to defeat Illinois Gov. Pat Quinn (D). The TPM Polltracker finds Rauner with a slim 0.3 point lead over Quinn.