Sen. John Thune (R-S.D.) (Chip Somodevilla/Getty Images)

If we could pick just one adjective to describe Donald Trump as a presidential candidate, it'd be: unpredictable.

Anytime he steps up to a microphone, anytime he's on a debate stage, anytime a reporter digs into his background, you never know what you're going to get. As The Fix's Chris Cillizza wrote back in February, Trump's unpredictability is Republicans' worst nightmare in a presidential nominee: How can they protect themselves from the political equivalent of a derecho, an apocalyptic-like weather event that hits with no warning?

They can't. Nothing has epitomized that better for down-ballot Republicans than these past six days. And perhaps no lawmaker has demonstrated this no-win scenario better than Sen. John Thune (R-S.D.), who in the span of a few days appeared to want Trump gone then indicated he'd vote for him. There are a handful of other lawmakers who have done the same, but in part because Thune is part of Senate Republican leadership, and in part because his comments on Trump have been so tortured lately, he's a great case study.

Here's a timeline of how one Senate Republican has responded to Trump's tumultuous week:

4 p.m. EST Friday: The Washington Post's David Fahrenthold publishes a tape of Trump on a TV set in 2005 bragging about being able to kiss, grope and have sex with women because he's a star. In a statement immediately after, Trump dismisses the talk as “locker room banter.”

11 p.m.-ish Friday: The furor continues. Trump releases a video statement: “Anyone who knows me knows these words don't reflect who I am. I said it. I was wrong. And I apologize.”

Noon Saturday: Despite Trump's apology, the wave of Republicans abandoning Trump in the wake of The Tape™ is at its crest. Four vulnerable Senate Republican candidates, including Sen. John McCain (R-Ariz.), say they can no longer vote for Trump.

12:51 p.m. Saturday: Thune becomes the highest-ranking Republican to call on Trump to step aside (which is the only way to get him off the ticket this late in the game).

1 p.m.-ish Saturday: Based in part on Thune's tweet, I write: Senate Republicans look ready to jump off the Trump bandwagon.

9 p.m. Sunday: Trump and Clinton meet on the debate stage in St. Louis for their second of three presidential debates. Trump apologizes for what he said on that tape and, after repeated questioning from CNN's Anderson Cooper, said he never sexually assaulted anyone.

Republican presidential nominee Donald Trump and Democratic presidential nominee Hillary Clinton sparred over video of Trump's lewd remarks and former president Bill Clinton's past scandals, Oct. 9 at the second presidential debate in St. Louis. (The Washington Post)

After acknowledging the tape, a lively Trump puts Clinton on the defense on everything from her emails to Benghazi to her husband's sexual indiscretions and how Clinton defended him. It was a stronger-than-expected — if not controversial — debate performance for Trump, though Cillizza still called Clinton the winner.

Democratic presidential candidates Clinton and Trump shake hands during the first presidential debate. (REUTERS/Carlos Barria)

Monday morning: House Speaker Paul D. Ryan (R-Wis.) tells his GOP colleagues he's breaking up with Trump. He won't rescind his endorsement, but he also won't campaign with or defend the GOP nominee, instead focusing his efforts on trying to save the Republican majorities.

Monday afternoon: The Wall Street Journal - NBC News poll is out, the first since the release of the tape, and it's a doozy for Trump: In a one-on-one race in a post-hot-mic-world, Clinton leads Trump by 14 points.

Tuesday morning: Trump starts a Twitter war against his own party, blasting high-profile Republicans who have ditched him.

Tuesday afternoon: A new Wall Street Journal - NBC News poll finds Clinton still leads Trump (by 9 points) but that Trump's debate performance managed to shore up Republican support for him.

Before the debate, 67 percent of Republican voters said they thought GOP House and Senate candidates should stand behind Trump. After the debate, that number was at 83 percent.

Tuesday night: Thune, back home in South Dakota, catches up with local media. He says the 2005 tape “was more offensive than anything that I had seen."

Even though he still wishes Trump would go, Thune appears to back off his comments to try to get him off the ballot, saying it's too late anyway: “We're several days past that now and the more days that past the harder it's going to be for somebody else to be able to step in and become the nominee and I understand that, but I still think that's the best solution.”

Then Thune indicates — but does not outright say — he'll be voting for Trump, telling a local reporter he plans to vote for every Republican on the ballot.

"[Trump] has a lot of work to do, I think, to win this election,” Thune said of Trump. “But I’m certainly not going to vote for Hillary Clinton.”

Wednesday afternoon: We at The Fix try to make sense of Thune's latest comments, writing that his latest position appears to mark a total reversal of his position just days earlier: “A reasonable reading of this situation is that Trump has managed to stop the bleeding among Republicans tempted to ditch him. … Thune's apparent reversal on Trump in a matter of days is Exhibit A.”

Wednesday evening: The New York Times publishes a story in which two women accuse Trump of sexual assault in two different instances. The Palm Beach Post publishes a report of another woman who accused Trump of groping her. The stories give new traction to other claims, including one published late Tuesday by the Los Angeles CBS affiliate, in which a woman who was Miss Arizona in a Miss USA pageant owned by Trump said Trump walked in on them while they were changing. (The Fix's Aaron Blake has a roundup of the latest.) Later that night, People magazine reporter Natasha Stoynoff posts a first-person account of Trump forcing himself on her in his mansion. Trump denies all the accusations.

Thursday morning: Silence from Thune and other congressional Republicans who had, less than 48 hours earlier, indicated they would vote for him.

To be continued ...