There are days when it seems impossible to write about the presidency of Donald Trump. Doing so requires contemplating facts and scenarios that, not so long ago, would have sounded like the worst sort of Alex Jones conspiracy-mongering. For example, we learned from The New York Times over the weekend that the FBI once opened an investigation into the president of the United States for possibly being an agent of Russia.

Really?

Really.

Obviously, this is not a complete surprise. Hillary Clinton warned us during the campaign that Trump was a puppet of Russia's Vladimir Putin. Special Counsel Robert Mueller has been investigating apparent links between Trump's campaign and the Russian officials who were working for Clinton's defeat. Then there was that crazy press conference with Putin just a few months ago. So, this weekend's report about the FBI investigation rated only as a minor bombshell.

Still, the news serves as a great opportunity to step back, take a deep breath, and consider a Trump presidency that, increasingly, reads like the plot of a lesser Tom Clancy novel.

Here are four things to consider as we continue to scrutinize Trump's relationship with Russia:

First, he might be innocent. Allegations and investigations are not the same as hard evidence, and it's possible that Trump is being smeared with some of the worst charges that you can aim at a president of the United States. Even if that's so, that doesn't necessarily make Trump a sympathetic figure — remember that he rose to political prominence on the strength of the false, racist "birther" theories meant to undermine President Barack Obama. Live by ugly conspiracy-mongering, and you can die by it, too.

Still, the best-case scenario for this president is that he's getting his just deserts. That should be alarming.

Second, maybe he's not innocent. We don't need to live by a "beyond a reasonable doubt" standard with the American presidency, and Trump long ago entered "walks like a duck" territory, as far as Russia is concerned. Just this weekend, The Washington Post reported that the president has been hiding the details of his meetings with Putin from even his closest aides. Combine that with the Times report, and even Fox News' Jeanine Pirro was forced on Saturday to ask the president an almost unthinkable question: "Are you now or have you ever worked for Russia, Mr. President?"

Trump didn't directly answer. Uh-oh. Alarm bells should be ringing.

Third, the damage could be catastrophic. If Mueller or Congress can reasonably prove a determination that Trump is a witting or unwitting agent of Russia, that taints every bit of governance that has occurred during the last two years — every treaty broken, every regulation scrapped, every judgeship filled and Cabinet appointment made, up to and including Vice President Mike Pence. How to undo that damage?

In all honesty, we probably can't — we can only rebuild. There might be pressure on Supreme Court Justices Neil Gorsuch and Brett Kavanaugh to resign their lifetime appointments, if only to keep the consequences of a tainted presidency from lasting for a generation. Short of impeachment, though, it seems unlikely that anybody will readily give up the power they have attained during this administration. The main thing Democrats can do is try to win elections, and to reconstruct laws, diplomatic relationships, and institutions from there.

Fourth and finally, the governance of the United States is in need of revamping. That's clear no matter how this ends. As currently constructed, it cannot protect us from the likes of Trump and the chaos he has spread. My colleague Ryan Cooper last week noted how the Constitution's design led almost inevitably to the current government shutdown. It's obvious now that our methods for vetting presidential candidates are also inadequate.

A requirement that presidential candidates publicly disclose their tax returns would be a good start, but it's possible we should go further: Before an individual publicly declares their candidacy, they should be required to undergo the same kind of formal, nonpartisan vetting and background check required of any other public official with a high-level security clearance. They should be able to do this privately — and there should be an appeal process if they disagree with the findings of that vetting. The bottom-line results of that vetting, pass or fail, should be made public when the candidate files for office.

There are problems with this approach: You don't want to give the intelligence community veto power over America's democratic choices. Right now, though, Americans can be forgiven for suspecting the president is less than fully committed to the country he leads. Without that confidence — in Trump and in his successors — we're doomed to endless crisis.