Presidents have had worse weeks than the one ending Donald Trump's first 100 days in office, but most of the examples I can think of include resignation and worse. So far this week (and he still has one more day!) Trump has retreated or been defeated on his Mexico wall, on NAFTA, on sanctuary cities, and on health care reform. The administration went through something like three positions on North Korea. Trump rolled out a tax reform "plan" that not only has been ridiculed from all sides, but is also basically dead on arrival; Trump's one-page of bullet points is vague enough that any Congressional product may resemble it, but he's not likely to be a significant player in shaping what House and Senate Republicans choose to do. Beyond that, Trump gave a series of interviews which mostly served to furnish up new humiliations for him, whether it was complaining to Reuters about how unexpectedly hard the job was or obsessing to AP about cable TV news. Other 100-days profiles featured White House staff and Trump friends basically saying the president is . a moron? \u201cIf you\u2019re an adviser to him, your job is to help him at the margins,\u201d said one Trump confidante. \u201cTo talk him out of doing crazy things.\u201d A toddler? Advisers have tried to curtail Trump\u2019s idle hours, hoping to prevent him from watching cable news or calling old friends and then tweeting about it. That only works during the workday, though\u2014Trump\u2019s evenings and weekends have remained largely his own. Also this week, investigations on the Trump-Russia scandal continued with new revelations about former National Security Advisor Michael Flynn, and a misfire by Ivanka Trump (rapidly walked back) reminded everyone of Trump's other big scandal involving conflicts of interest, nepotism, emoluments, and more. I suspect I'm missing a few more. The good news? It's always possible Trump could at least somewhat turn it around. He could hire a real chief of staff empowered to clean up the White House. He could start doing the work he's supposed to be doing - learning about policy and process. Yes, he does have some potential assets to build on if he is capable of doing so. For that matter, he could still divest his holdings and put an end to what is basically a lawless presidency. Realistically, however? What's happening is exactly what anyone with any sense knew what would happen if he became president - indeed, I agree with Ross Douthat that we've been relatively lucky that it hasn't been worse. We can hope he'll improve as he goes along, but there's really no sign of it so far, and no realistic reason to expect it. You May Also Want To Watch: So what's the big lesson in Trump's first 100 days? It's the same one that's been obvious all along: Republican party actors should have done whatever it took to defeat his nomination when they had the chance. Nominations matter, and none more so than the presidential nomination, and they are worth fighting - hard - over. That's mainly because a party only gets so many opportunities at the presidency, and it's a disaster for groups within the party to waste them - think Jimmy Carter and the Democrats' failure to achieve important policy goals in 1977 to 1980. It's also because of the electoral damage an unpopular presidency can inflict on the party, as we've seen in the last three midterm elections. And it's because presidential nominations are part of defining and (re-)creating the party itself, so that once a party is stuck with a nominee they are stuck with whatever that nominee does. Especially if that nominee wins the White House. As a result of Trump, some groups will be elevated within the Republican Party and others will be sidelined; the party will come to stand for some policies and not others; some individuals who rose with Trump will be empowered within the party or at least become credentialed as high-profile representatives of the party for years, maybe decades, to come. We'll never know whether another Republican would have won the 2016 election or not. We'll never know how, as a worst-case scenario for defeating Trump, how an ugly convention with the party "stealing" the nomination from him would have played out. My guess is it would have been just fine; Trump's a paper tiger, and those who swore they were loyal to him would have wound up happy to support any nominee against Hillary Clinton. I certainly can't prove that, however. But it doesn't matter. Nominating Donald Trump damaged the Republican Party, with the only remaining questions having to do with how bad that damage is. Party leaders let everyone else down by letting this happen. They deserve the blame, and their successors need to learn from this: Never again.