McCain on one of his last days on Capitol Hill. Photo: Brendan Smialowski/AFP/Getty Images

After fighting brain cancer for more than a year, John McCain has decided to discontinue treatment for the illness. “Last summer, Senator John McCain shared with Americans the news our family already knew: He had been diagnosed with an aggressive glioblastoma, and the prognosis was serious,” the senator’s family said in a statement. “In the year since, John has surpassed expectations for his survival. But the progress of disease and the inexorable advance of age render their verdict. With his usual strength of will, he has now chosen to discontinue medical treatment.”

McCain has been absent from the Senate since December 2017. Since then, he has made occasional, rhetorical interventions into national politics — often in the form of statements criticizing the current Republican president. His most consequential political action in 2018, however, was his decision not to resign from his Senate seat before June 1. Had he stepped down before that date, Arizona voters would have chosen his replacement in a special election this fall. Now, upon McCain’s passing, Arizona’s Republican governor Doug Ducey will appoint an interim successor, who will serve in the Senate through (at least) 2020.

McCain famously turned down the opportunity to escape detention as a prisoner of war in Vietnam, to maintain solidarity with his fellow-prisoners. His long career in politics included a stint as the Republican Party’s standard-bearer in 2008. Through much of his time in Washington, McCain demonstrated a greater capacity for independent thought and action than his Republican counterparts. The senator voted against George W. Bush’s tax cuts on the grounds that they were regressive, and co-sponsored legislation intended to limit the influence of concentrated money on American politics. In his last years in Congress, McCain evinced less interest in bucking his party’s orthodoxy — but his vote against repeal of the Affordable Care Act last summer might have been the most consequential “maverick” move of his career.