Tuesday, Trump and McCain have been in a war of words about McCain's comments. The post has been updated below.

Since President Trump was sworn in, Sen John McCain (R-Ariz.) has been one of his chief antagonists in the Senate.

But over the past few months, McCain has amped up his criticism of the president to a level rarely seen in recent, intra-party political battles.

While accepting an award for bipartisanship Monday night in Philadelphia, McCain excoriated Trump's internal-looking foreign policy as a “half-baked, spurious nationalism cooked up by people who would rather find scapegoats than solve problem.”

McCain is in a season of speaking his mind more than usual. Over the summer he announced he was diagnosed with a deadly form of brain cancer. He told CBS's "60 Minutes” that he's “more energetic and more engaged as a result.”

“I know that I've got to do everything I can to serve this country while I can,” McCain said.

Apparently to McCain, that means warning his party and his country of about President Trump as clearly as possible. At this point, his message is evident: He doesn't think Trump is a good leader, and he thinks Republicans should stand up to him. Judging by recent events, some of his colleagues seem to be listening.

Trump responded in a radio interview by appearing to threaten McCain with retaliation: "It won't be pretty." McCain responded on CNN: "I've faced far greater challenges than this."

Here are seven biting recent criticisms of the Trump administration from McCain.

1. “We’re getting nothing done. All we’ve really done this year is confirm Neil Gorsuch to the Supreme Court.” — July 25 speech on the Senate floor

Sen. John McCain (R-Ariz.) on July 25 addressed senators days after being diagnosed with brain cancer. He said the Senate has become too partisan. (U.S. Senate)

McCain gave this speech shortly after his diagnosis was announced, and shortly before he would be one of the deciding votes to kill Republicans' health-care bill. It's an indictment of Congress, yes, but also arguably the president, who has demonstrated he is very sensitive to blame being directed his way for Republicans' dearth of legislative victories.

2. “We are an important check on the powers of the executive. Our consent is necessary for the president to appoint jurists and powerful government officials and in many respects to conduct foreign policy. Whether or not we are of the same party, we are not the President’s subordinates. We are his equal!" — July 25 speech on the Senate floor

It's crystal clear what he's saying to his colleagues here: Stand up to the president when you think he's wrong.

3. “We don’t covet other people’s land and wealth. We don’t hide behind walls. We breach them. We are a blessing to humanity.” — July 25 speech on the Senate floor

This appears to be a dig at one of Trump's most iconic legislative priorities, building a wall on the U.S.-Mexico border.

4. “There is nothing in their hate-driven racism that can match the strength of a nation conceived in liberty.”Aug. 31 op-ed in The Washington Post.

McCain, like many Republican lawmakers, felt compelled to directly contradict the president's sympathy for some protesters marching alongside white supremacists and neo-Nazis in Charlottesville

5. "[W]e have to respect each other or at least respect the fact that we need each other. That has never been truer than today, when Congress must govern with a president who has no experience of public office, is poorly informed and can be impulsive in his speech and conduct." --- Aug. 31 op-ed in The Washington Post

McCain's attacks are starting to get more personal. Here he's going after the president's experience, character and leadership abilities.

6. “We must respect his authority and constitutional responsibilities. We must, where we can, cooperate with him. But we are not his subordinates. We don’t answer to him. We answer to the American people.” — Aug. 31 op-ed

By now this is a recurring line in McCain's criticisms of the president. He is basically advising all of Congress to prioritize its own relationships over its standing with Trump and rallying GOP resistance against him for the sake of the country.

7. “To fear the world we have organized and led for three-quarters of a century, to abandon the ideals we have advanced around the globe, to refuse the obligations of international leadership and our duty to remain “the last best hope of Earth” for the sake of some half-baked, spurious nationalism cooked up by people who would rather find scapegoats than solve problems is as unpatriotic as an attachment to any other tired dogma of the past that Americans consigned to the ash heap of history.” — Philadelphia, Liberty Medal award ceremony from the National Constitution Center.

McCain isn't the first senator to call on his colleagues to be a bulwark against Trump. His Arizona colleague, Sen. Jeff Flake (R), did so before him. Flake arguably has a lot more to lose than McCain for speaking out against Trump. He is now facing a primary challenger boosted by pro-Trump allies after he wrote a book criticizing his party's “tremendous powers of denial” that led to the rise of Trump.

But McCain's words arguably carry more weight. He is a senior statesman who ran for president himself. He played an outsized role in Trump's campaign in ways he likely wishes he hadn't. And since being diagnosed with brain cancer, he's taken several opportunities to warn his party not to get complacent with Trump.

McCain's opposition to the president isn't just words. Twice, he has been one of the deciding votes to kill a health-care bill that Trump very much wanted passed.

Other senators are listening. Sen. Bob Corker (R-Tenn.) recently announced he's retiring and then accused Trump of leading the U.S. “on the path to World War III.”

When you combine their voting records on major issues with their rhetoric, Corker, McCain and Flake are among the most critical GOP senators of Trump.

It's an open question if there will be more senators to follow McCain's, Flake's and now Corker's lead to be the party's anti-Trump voice. But if there are, we could look back on their anti-Trump arguments, laid out less than a year into Trump's presidency, as one of its turning points.