...The point of the Nixon comparison is that the argument that Trump shouldn't be impeached because "it would divide the country" is spurious, at best...
I'm not sure I agree with that and I have read opinions of people who do not agree at all. The Republican-elected president previous to Nixon was Dwight Eisenhower. The Republican-elected president after Nixon was Ronald Reagan. I think it can be argued that Watergate -- and Nixon essentially being forced out of office -- left a bitterness and a resentment among Republicans that continues to this day.
I think it can be argued that post-Nixon/Watergate the Republican Party became noticeably more callous and cynical. Some of the most partisan Republicans, like Gingrich, Cheney, Rumsfeld, all entered politics in that era.
Below is a quote from Geoffrey Kabaservice, an author and research director of the Republican Main Street Partnership.
Nixon was, despite the popular conception of him today, a centrist Republican—and because of Watergate, he may have been the last one. Nixon’s sensibilities were populist-conservative, but operationally he acted as a moderate and even occasionally as a progressive, for example when he created the Environmental Protection Agency and proposed national health insurance that would have covered more people than Obamacare. In 1997, I interviewed Elliot Richardson, who as attorney general played a key role in bringing down Nixon but felt history had wrongly remembered the 37th president. “Most people don’t really get the fact that the Nixon administration was to the left of the Clinton administration,” Richardson told me.
Politico link