As a first-term senator in 1987, he met with federal regulators on behalf of a donor and savings-and-loan chairman. The ensuing Keating Five scandal, which stretched from 1989 to 1991, was a public humiliation for Mr. McCain, a real blow to someone who lived by a stringent honor code.
The only Republican implicated, he also received the most lenient finding by the ethics committee, which found him guilty of poor judgment. The televised hearings essentially ended the political careers of several of the other senators involved. But that searing experience drove Mr. McCain to become a more independent lawmaker as well as a champion of campaign finance changes intended to reduce the influence of big money in politics, and he eventually became his party’s presidential nominee in 2008, after a failed bid in 2000.
The loss to Barack Obama that followed rocked Mr. McCain, and he returned to the Senate unhappy and somewhat at a loss. But he eventually recovered his footing and remained an outspoken force on immigration and the military — and an outspoken opponent of the Obama administration on a variety of domestic and foreign affairs issues.
Few in the Senate escaped Mr. McCain’s outbursts of temper, and he could be extremely cutting and dismissive to those he saw as standing in his way or offering what he considered unfounded views. During his presidential run in 2008, some of his colleagues whispered concerns that his temper was potentially disqualifying. But the episodes often quickly passed, and Mr. McCain would offer apologies.
For a man who built his public reputation through close ties to journalists, he could also be up and down with the news media. But even when angry, he had a hard time keeping himself away and thoroughly enjoyed jousting with the reporters who frequented the Capitol hallways.
When he first returned to Washington in September after his devastating diagnosis, reporters were encouraged to stay far away from him to avoid passing on any illness, given his weakened immune system. That lasted about a day, and soon Mr. McCain was striding through the Senate hallways as usual, trading barbs and bits of information with journalists and colleagues who were aware that their moments with him were drawing to a close.
The final elections of his career marked a turn to the right for Mr. McCain as he sought to fight off the Tea Party movement, a groundswell he helped accelerate with his selection of Sarah Palin as his vice-presidential nominee in 2008. But in one of his last acts, he defied the far right — and President Trump, the man who had ridiculed his capture in Vietnam — by helping to derail the Republican drive to overturn the Affordable Care Act.