Sen. John McCain (R-AZ) revealed that he will not seek reelection in an excerpt from his book published Monday, according to a Tuesday CNN report.

“This is my last term. If I hadn’t admitted that to myself before this summer, a stage 4 cancer diagnosis acts as ungentle persuasion,” he said. “I’m freer than colleagues who will face the voters again. I can speak my mind without fearing the consequences much. And I can vote my conscience without worry.”

McCain’s dire prognosis last summer has reportedly caused whispered worry within the Republican party at the prospect of defending another Senate seat in an unfavorable election environment. Democrats in the Arizona senate blocked Republicans’ recent attempt to ensure that McCain’s seat is kept off the ballot in November if he leaves office.

It is still unclear when McCain’s seat will be up for election, though according to the AP, it would be on this year’s ballot if he leaves office by May 30 under current law.