When news broke last night that Sen. John McCain, Republican of Arizona, has been diagnosed with an aggressive form of brain cancer, an incredible bipartisan wave of support broke across the Internet.

Whether you’re a Democrat or a Republican, and whether you agree with McCain on policy issues or not, he’s a role model and a public servant who has served his country for more than 60 years–as a Navy officer, a prisoner of war, and a United States senator and presidential nominee.

McCain is also a true leader. Stepping through his personal history, it’s easy to find example after example of the kinds of things that great leaders learn to do–and that they teach others to do, as well. Here are seven of the most striking examples.

1. They stand up for the little guy.

This story goes all the way back to 1955, when McCain was a Naval Academy midshipman, and an older, higher-ranking cadet was picking on an enlisted sailor. Although McCain was outranked by the other cadet, and risked getting in trouble, he stood up to the higher-ranking mid. Doing things like this cost him; McCain ultimately graduated 894 out of 899 in his class.

2. They act with civility.

There are many examples. One of the most famous came in 2008, when McCain was running against then-Sen. Barack Obama for the presidency, and a woman asking a question called Obama “an Arab” (as a pejorative, which is of course a whole additional issue). McCain responded by taking the microphone away from her and saying that Obama was “a decent family man and a citizen that I just happen to have fundamental disagreements with.”

3. They demonstrate bravery.

McCain spent five-and-a-half years as a prisoner of war during the Vietnam War, and was tortured for much of that time. He spent two full years in solitary confinement. Both McCain’s father and grandfather were Navy admirals before him, and when his captors realized he was from a high-ranking military family, they sought to send him home ahead of other prisoners. McCain bravely refused to leave the others, and his torture was intensified for years as a result.

4. They act with determination.

McCain had been a Navy fighter pilot, but he came home with severe physical injuries after being a POW. For one thing, he couldn’t lift his arms over his head. Nevertheless, he pushed to remain in the Navy and endured years of utterly grueling physical therapy sessions to be able to stay on active duty. (As one biographer wrote, it helped that the Navy had never anticipated that an officer who couldn’t lift his arms would try to remain a fighter pilot; thus there wasn’t a specific rule against it.)

5. They accept blame.

McCain’s first marriage fell apart after he came home from Vietnam, but he refused to blame the war and his imprisonment–rather implicitly admitting he had been unfaithful. “My marriage’s collapse was attributable to my own selfishness and immaturity more than it was to Vietnam, and I cannot escape blame by pointing a finger at the war,” he later said. “The blame was entirely mine.”

(In fairness, McCain has been remarried since 1980, and has seven children.)

6. They seek to serve.

I suppose this can be said for many politicians (notwithstanding the current low level of esteem in which the public holds them at large). But when it became clear his physical challenges would preclude him from reaching the highest posts in the Navy, he began a political career that has lasted almost 40 years so far.

7. They stick to their principles.

Many people who are voicing sympathy for McCain as he faces this health issue don’t actually agree with his politics–liberals who think he’s too conservative, and conservatives who think he’s not conservative enough. But regardless, McCain has stayed true over four decades to his own principles. There are many examples, but one that can’t be forgotten now is that he renounced future-President Trump’s endorsement in October, after the infamous Access Hollywood tape was released.

Note: This column isn’t intended to be a political endorsement of McCain. But in the interest of disclosure, I should acknowledge that a very long time ago, I went on one or two dates with McCain’s press secretary. Also, I donated to his presidential campaign back in 2000. I can’t remember which of these events came first.

The opinions expressed here by Inc.com columnists are their own, not those of Inc.com.