The one consistently correct prediction about the Republican primaries this year was that your best guess as to what happens next was probably wrong.

While the Democratic race largely fell into line with early expectations – Hillary Clinton fending off a challenge from the left – the Republican primary has been chaos from its first moments. It feels like every time polls, fundraising, and news coverage start to point one direction, things swerve in another: Front-runners turn into underdogs and then disappear entirely; candidates branded as novelties turn into political powerhouses; and broad theories of how modern American politics work are tested to their limits.

RELATED: Lindsey Graham, the GOP’s prophet of doom, departs the race

We compiled a sampling of once-popular assumptions about the GOP race that have been overtaken by events in 2015. As you might expect, one candidate in particular tends to dominate the list.

“The biggest mistake in conventional wisdom was thinking Donald Trump would fade,” GOP strategist Ari Fleischer told MSNBC.

Close video Clinton vs. Trump: Preview of the main event? This week we’ve seen the two dominant forces in Presidential politics - Donald Trump and Hillary Clinton - matching jab for jab. What could be next year’s marquee match-up may already be in round one. NBC News’ Hallie Jackson, the Washington Post’s… This week we’ve seen the two dominant forces in Presidential politics - Donald Trump and Hillary Clinton - matching jab for jab. What could be next year’s marquee match-up may already be in round one. NBC News’ Hallie Jackson, the Washington Post’s… share tweet email Embed

One caveat before we begin: This isn’t about making fun of bad predictions (though there are some in here). It’s about the ways the primary has played out against expectations and why that turned about to be the case. Political analyst Charlie Cook summed the dynamic up nicely in an email to MSNBC.

“Was there an expectation early on that Jeb Bush would lock up the conventional, establishment side of the Republican and have an excellent chance of winning the GOP nomination? Yes,” Cook said. “Do we now see why that did not happen? Yes. Was it knowable nine months ago? Not really.”

To the extent people have blown it on the prediction front, this reporter is plenty guilty himself.

Okay, let’s begin …

The GOP nominee will likely be a governor. This was a popular refrain among Republican elites throughout 2014 and into early 2015. The party resented President Obama’s lack of experience, the country hated Congress, and the GOP had plenty of popular governors on their bench, so obviously a state executive made sense to win the nomination. With the recent exception of 2008, history tilted toward gubernatorial nominees in general. Instead the desire for change has eclipsed the desire for experience, and the four highest-polling candidates are first term Sens. Marco Rubio and Ted Cruz and political outsiders Dr. Ben Carson and Donald Trump.

RELATED: In southern swing, Cruz looks to regain offensive against Rubio

Rand Paul is a serious threat to win the nomination. Well before Trump entered the race, political observers saw plenty of potential for an unorthodox candidate to steal the nomination. They just thought the most likely culprit was Sen. Rand Paul. In fact, this time last year The Washington Post’s Fix blog ranked him most likely to win the nomination (second place: New Jersey Gov. Chris Christie). The possibility was real enough that several GOP hawks threatened to run long shot presidential campaigns mainly to confront Paul in debates.

Their fear was that Paul would incorporate Ron Paul’s libertarian base into a broader conservative coalition by jettisoning some of his father’s more fringe ideas. Instead, he ended up awkwardly straddling the line between both groups and has yet to play a meaningful role in the race.

The debates were the problem in 2012 . One frequent complaint among Republican leaders after Mitt Romney lost was that the large number of debates and their mainstream media moderators hobbled the nominee by forcing him to the right on immigration, playing up divisive questions, and encouraging underfunded insurgents to attack the front-runner.

The RNC reined in the number of debates and exercised greater control over their format, but it turns out something deeper might be the issue. When the curtain rose on the first debate in August, the fights were nasty and the clashes with moderators – in this case, from Fox News – were as intense as ever. More recently, squabbling over immigration at debates have dragged candidates like Sen. Ted Cruz to Romney’s right. Maybe the debates weren’t the problem?

RELATED: Ted Cruz on defensive as immigration fight engulfs campaign

Jeb Bush will keep Marco Rubio out of the race. This tongue-in-cheek 2014 column aside, Bush wasn’t widely considered an unstoppable front-runner when he announced he was exploring a presidential bid. But some did assume his “shock and awe” fundraising would at least scare off potential rivals with similar appeal. In particular, many observers suggested Rubio, who relied on a similar network of Florida donors and whose path to the nomination also rested on consolidating establishment support, would run for re-election instead rather than face his old mentor. He took the plunge and his current odds look better than Bush.

Scott Walker is the perfect Iowa candidate. As a socially conservative Midwestern governor who was raised partially in Iowa and led early polls of the state, Walker seemed like an obvious fit. “Scott Walker is the runaway front-runner in Iowa,” one Iowa Republican told Politico in July. “The only news at this point would be if he didn’t win the state.” Just two months later he dropped out after falling victim to a variety of self-inflicted campaign wounds.

Super PACs will dominate the race. The assumption that unlimited outside spending would play an unprecedented role in the 2016 campaign was correct, but not in the way many anticipated.

Bush’s ally Right to Rise raised an unprecedented sum of over $100 million, and many assumed (including Bush himself) that outside advertising would give him a major advantage in the race. Instead, Bush and his supporters have spent $38 million on ads since September, more than double anyone else, with few signs of improvement. At the same time, Trump renounced super PACs and barely ran any ads at all, instead using his constant press coverage and social media to get his message out.

RELATED: No one won the Republican debate. Now what happens?

While the ads have been the dog that didn’t bark, super PACs and dark money groups that conceal donors played much bigger roles this year in managing tasks that were once the exclusive purview of campaigns themselves. Mother Jones’ Tim Murphy described in a must-read feature this month the numerous ways big money groups now act as an “uncampaign” that’s often barely distinguishable from a candidate’s official operation.

Close video Donald Trump leads in new poll NBC’s Hallie Jackson, MSNBC’s Steve Kornacki, and Matt Lewis, author of ‘Too Dumb to Fail,’ join Thomas Roberts to discuss the controversy regarding comments Donald Trump made about Hillary Clinton, plus more on the GOP field. NBC’s Hallie Jackson, MSNBC’s Steve Kornacki, and Matt Lewis, author of ‘Too Dumb to Fail,’ join Thomas Roberts to discuss the controversy regarding comments Donald Trump made about Hillary Clinton, plus more on the GOP field. share tweet email Embed Buzzfeed reporter McKay Coppins’ 2014 theory that Trump would never leave good money on the table to run for president sounded pretty convincing. After all, Trump ended his 2011 flirtation with running on a birther platform to stick with “The Apprentice.” Whether it was to spite Coppins or to Make America Great Again, the biggest sign Trump was serious this time came after he surprised his skeptics and announced he was leaving his popular show.

Trump is running, but it’s a nonstarter because Republicans hate him. One reason so few people saw Trump’s surge coming is that polls frequently indicated voters, including Republicans, disliked him personally by wide margins nationally and in early states Iowa and New Hampshire. The week he announced his run, a national NBC/WSJ survey of Republicans put him at 1% support and found 66% of GOP respondents said they were unlikely to ever consider voting for him, the worst number in the field. Days earlier, a Monmouth poll put him at 2% support. The data spawned articles like “Why Donald Trump Isn’t A Real Candidate, In One Chart” on FiveThirtyEight. That was the old Trump, though, and his decision to center his campaign around nativism opened up a deep vein of conservative support.

RELATED: The super-complicated Rubio-Cruz immigration fight explained

Trump is leading – and that’s great news for Jeb Bush! Generals always fight the last war. After Trump surged to the front of the polls, many Bush supporters assumed the phenomenon actually helped the former governor. The New York Times described the mood in August as “all but giddy” and reported that his top strategists saw Trump as “nothing short of a godsend.”

The thinking was that Trump was not a serious threat to win the nomination, but could prevent more plausible conservative challengers like Walker from taking root while Bush quietly consolidated establishment support. The obvious precedent was Mitt Romney, who happily waited out surges from fringe rivals like Michele Bachmann and Herman Cain while saving his firepower for more credible threats like Rick Perry. Trump helped knock out Walker, but his withering attacks on Bush’s “low energy” dragged him down as well and he’s still scrambling to respond effectively.

Donald Trump is finished because …

… he disparaged prisoners of war. Republican leaders lined up to criticize Trump en masse in July after he said Sen. John McCain were “not a war hero” because he was captured during the Vietnam War. Since there’s no political constituency for bashing POWs, it stood to reason this would damage Trump. This was the first of many times Trump would upend the usual rules of politics.

RELATED: Five big takeaways from the GOP debate

… he attacked Megyn Kelly and feuded with Fox News. Trump earned another wave of conservative criticism after Trump said that Fox host Megyn Kelly had “blood coming out of her…whatever” when she moderated the GOP debate earlier that week. Red State editor Erick Erickson barred Trump from a candidate showcase and predicted it was “the beginning of the end” for the early frontrunner. As Nate Silver pointed out, common sense and data both confirmed Fox News was wildly popular with Republicans. There was no way Trump could win a feud with the network. Except he did – Fox executives worked out a ceasefire and Trump continued to insult Kelly every few weeks anyway without repercussions.

“When Trump said McCain wasn’t a hero and then when he accused Megyn Kelly of blood out of orifices, both those times I thought he was finished,” GOP fundraiser Fred Malek told MSNBC. “I’ve been dramatically wrong in his expected demise.”

… the Paris attacks will expose his dangerous foreign policy ignorance. Republican leaders predicted Trump would fade after the Paris terrorist attacks refocused the race on security. After all, how could voters worried about further violence from radical Islamic groups trust a candidate who seemed completely uninterested in learning even the basics of Middle East policy? Instead, he proposed a ban on Muslim travel and surged to his highest point yet in national polls.

We could go many more rounds on this subtopic alone (he called Iowans “stupid!”). Instead, we’ll end our piece with an Onion article: “’This Will Be The End Of Trump’s Campaign,’ Says Increasingly Nervous Man For Seventh Time This Year.”