The president tweeted Monday: "Most politicians would have gone to a meeting like the one Don Jr attended in order to get info on an opponent. That's politics!" This was a shortened version of the answer the president gave during his press conference with the French President last week. "Politics," he said, "is not the nicest business."

He's right. Politicians have done some grim things in pursuit of the office. President Franklin Roosevelt was a philanderer, nevertheless, he pushed aides to use his opponent Wendell Wilkie's affairs to hurt him. He even tutored aides on how to spread rumors without getting caught. "We can't have any of our principal speakers refer to it, but people down the line can get it out," he said.

In 1968, then-candidate Richard Nixon worked with the South Vietnamese to slow the peace talks in Paris. Had they gone forward, Nixon thought the prospect for an end to hostilities would help his rival Hubert Humphrey. Nixon denied this, but John Farrell in his new book on Nixon has the goods. H.R. Haldeman, Nixon's right-hand man, was taking notes with the other hand. In the notes, Haldeman records Nixon’s orders to work through their channels to slow peace progress.

But there have also been times in politics when people did the opposite: behaving morally when it was easier not to.

In 1964 when Johnson's aide Walter Jenkins was arrested for soliciting sex in a YMCA bathroom, his Republican rival Barry Goldwater's staff wanted to make it a character issue in the campaign. Goldwater said no. He didn't want to ruin Jenkins. In 2000, Tom Downey, a top aide to Democratic nominee Al Gore, received his rival George W. Bush's debate briefing book. He turned it over immediately to the authorities. In 2008, Senator John McCain forbid his staff from using an ad that referred to his opponent Barack Obama's inflammatory former pastor Jeremiah Wright or from raising that issue in any other way. He believed it was a sneaky way to use Obama’s race against him.

In 1968, Johnson and his team knew what Nixon was up to. They had wiretapped the South Vietnamese ambassador who was in touch with the campaign through a contact nicknamed The Dragon Lady. (Music promoter Rob Goldstone is not the only exotic character in these tales). A couple days before the election, the Christian Science Monitor had the story of Nixon's behind the scenes work. Their correspondent in Saigon had come up with the reporting, but the paper needed the White House to confirm. (How quaint.)

Johnson, down on his ranch in Texas, held an emergency phone call with his Secretary of State and Defense. Should they confirm the report? They knew the story was true. They had the covert information. The president's men said it would be immoral to expose Nixon. "I do not believe that any president can make any use of interceptions or telephone taps in any way that would involve politics," said Secretary of State Dean Rusk. "The moment we cross over that divide, we're in a different kind of society."

Secretary of Defense Clark Clifford added his own reason: "I think that some elements of the story are so shocking in their nature that I'm wondering whether it would be good for the country to disclose the story and then possibly have [Nixon] elected. It could cast his whole administration under such doubt that I would think it would be inimical to our country's interests."

Clifford, who was a staunch Democrat (he helped orchestrated Truman's 1948 miracle comeback) was worried about the country more than defeating Nixon. The story never ran.

Politics is not the nicest business, but there are still times when people do the right thing.

It was this moral plane on which the president's team once defended against questions of Russian collusion. A month after Trump Jr.'s June 2016 meeting, when Jake Tapper asked the president's son if anyone in the Trump team had been in contact with the Russians as the Clinton campaign had suggested, he reacted with outrage. "It's disgusting," said Trump Jr. "It's so phony.” I can't think of bigger lies than when Kellyanne Conway in December said that it was "dangerous" to even suggest that any meeting between a Trump staffer and a Russian seeking to interfere in the election had taken place. The Vice President, when asked the same question, had a short unequivocal answer: "Of course not."

The defense against the collusion charge has, until now, been based in part on morals: No one in the Trump orbit would do such a thing. That insistence in the past would seem to make unavailable the defense now that a meeting of precisely the kind that was being asked about is now to be considered no big deal.

The president isn't entirely behind his own defense of his son. While on the one hand he says a meeting with someone advertised as a "Russian government attorney" bringing "sensitive information as part of Russia and its government's support for Mr. Trump," should be considered simple politics, the president and his lawyer insist that President Trump knew nothing of the meeting. The effort to create distance from the meeting makes it hard to accept that the thing at the end of the 10-foot pole is a nothingburger.

Would most politicians have gone to a meeting with someone advertised as being an agent of the Russian government? It's unlikely that many of the president's supporters who hold public office are now going to admit they'd seek to collude with an American enemy that interfered with an election. But even at the time of Trump Jr.’s meeting in the summer of 2016 there would have been a good reason for caution. It was GOP doctrine that Russia was an American enemy. Mitt Romney had named Russia America's number one geopolitical foe.

For this reason alone, members of the president's own team would probably not have taken the meeting as the president says. Reince Priebus and Sean Spicer wouldn't have taken the meeting. They were at the RNC when the party mocked Obama for underestimating the Russian threat again and again and then mocked Hillary Clinton for the same. Kellyanne Conway's political instincts probably would have kept her away too. It's unlikely the president's lawyer Jay Sekulow would have taken the meeting because his book last year, Unholy Alliance: The Agenda Iran, Russia and Jihadists Share for Conquering the World, was going to press when the meeting took place. Putin is on the cover.

Whatever one may think of how Trump Jr., Paul Manafort, and Jared Kushner should have behaved in accepting the June 2016 meeting, President Trump has updated its relevance to the present. It is now a moral benchmark for the president and his team. Despite the moral and national security reasons to be wary of such a meeting, by the president’s rules of politics it was still a fine thing to do.