About a month ago, conservative commentator Erick Erickson wrote a post at RedState headlined, "Ted Cruz vs. Marco Rubio: This Is Where We Are Headed." Erickson predicted that eventually, "the more conservative elements" of the party would fall behind Cruz, while "the more establishment elements" would opt for Rubio. It was a bold statement, considering that both candidates were stuck in the single digits in the polls.

After Wednesday night's third Republican debate, it's much easier to see how it could happen.

Rubio swatted away an attack by his main rival for establishment support, Jeb Bush, leaving the brother and son to former presidents looking petty and small. Not long afterward, Cruz opened fire on the debate moderators, winning wild applause from the crowd and praise from conservatives online.

Throughout the night, both gave crisp, clear, and rhetorically impressive answers, far outshining the other candidates on stage. The consensus in the vast majority of the political media — conservative, liberal, and nonpartisan — was that Cruz and Rubio won.

And though the polls still show Donald Trump and Ben Carson on top, even before Wednesday night, it's become increasingly common for commentators to theorize that Cruz and Rubio are on the rise — and will end up being the two most formidable contenders for the nomination. After this debate, that theory will only become more popular. Here's why.

Rubio buried his main rival, Jeb Bush

Rubio stood out first. After strong performances in the initial two debates, he was already viewed as on the rise — especially since onetime sorta-establishment favorite Jeb Bush's campaign has been floundering.

Lately, Bush has seen Rubio as his biggest threat. So after Rubio responded to a question from a moderator about the number of Senate votes he's been missing, Jeb tried to take him on. "Just resign and let somebody else take the job," he suggested.

Rubio's response was devastating. He started by pointing out that John McCain missed a huge amount of votes during his 2007-'08 presidential campaign, and Bush didn't seem to mind. "I don't remember you ever complaining about John McCain's vote record," he said. "The only reason you're doing it now is because we're running for the same position. Someone convinced you attacking me is going to help you."

The response had the ring of truth to it — the vote-missing attack is a phony and opportunistic one — but it was that final line above that really made Rubio seem above the fray. You're doing this because you're losing, Rubio implied, and even you don't really believe it.

Rubio easily got the better of the exchange, and it could strengthen an already-growing sense among GOP insiders that Bush just isn't up to the task. Rubio's main task in this debate was to prevent Jeb Bush from bringing him down a peg, and he accomplished it easily.

Cruz scorched the moderators

Later on, it was Ted Cruz's turn to shine — and he did it with the vintage Newt Gingrich 2012 move of attacking the debate moderators.

"The questions that have been asked so far in this debate illustrate why the American people don't trust the media," he said. "This is not a cage match. You look at the questions — Donald Trump, are you a comic book villain? Ben Carson, can you do math? John Kasich, will you insult two people over here? Marco Rubio, why don't you resign? Jeb Bush, why have your numbers fallen? How about talking about the substantive issues?"

It was a "moment" of the sort Cruz lacked in the first two debates. The audience applauded wildly — he was saying exactly what many conservatives across the country were thinking. And GOP pollster Frank Luntz's focus group loved it:

Ted Cruz's focus group dials hits 98 with his attack on media bias. That's the highest score we've ever measured. EVER. #GOPDebate — Frank Luntz (@FrankLuntz) October 29, 2015

Stylistically, Cruz performed strongly for the rest of the debate too — he didn't seem too angry, and even cracked a few jokes.

The case for Cruz versus Rubio

So far in this GOP campaign, political observers have been absolutely terrible at predicting what would happen next. So definitely take the following with many, many grains of salt.

But in recent weeks, more and more commentators have been moving toward Erickson's belief that both Rubio and Cruz are on the rise.

Already, the betting markets — a good measure of the current conventional wisdom — view Rubio, and not Bush, as the favorite to win the nomination. The New York Times's Ross Douthat called him the "unusual front-runner" last weekend, and Vox's Ezra Klein has predicted that Rubio will win eventually. This is mainly because despite a big advantage in both cash and name recognition, Jeb Bush has failed to catch on so far — and Rubio seems to be the obvious alternative.

The logic for a Rubio candidacy — he has a fresher name and face, he's more charismatic, he could well be a stronger general election contender — has been looking more and more persuasive. Neither party elites nor voters have fallen behind Rubio yet, but it seems to commentators like this is the obvious thing for them to do.

Predictions of a Cruz surge have been offered more gingerly. The basic assumption is that Trump and Carson are both doomed, and that Cruz will eventually inherit their support, since he's a more experienced politician who seems to be putting together a more serious campaign operation (with some seriously impressive fundraising from both big donors and the grassroots). He's positioned himself as tough on unauthorized immigration, which could please some Trump fans, and he's also built close ties to religious right groups, whose supporters currently like Ben Carson a lot.

"FACT: Ted Cruz is running the best campaign of any presidential candidate," the Washington Post's Chris Cillizza wrote this week. "If I had to put money on a delegate leader coming out of Super Tuesday, it would be Cruz," RealClearPolitics' Sean Trende tweeted. And some other commentators who once affirmatively proclaimed that Cruz couldn't win — because he was too despised by party elites — are now less sure.

Reasons to be more skeptical

On paper, all this makes a ton of sense. But little about this campaign has resembled what makes sense on paper.

Nobody foresaw the months-long poll domination of Donald Trump, many commentators have prematurely declared his collapse, few expected Ben Carson to surge in the polls after the first debate, and many predicted Scott Walker would be one of the most formidable contenders. (Walker quit the race more than a month ago.)

So, yes, prediction is very difficult, especially about the future. More specifically, both Cruz and Rubio have weaknesses that could hold them back.

Jeb Bush's Super PAC still has tens of millions of dollars it could spend trashing Rubio's reputation — and other attacks might not be swatted away so easily as the one on Rubio's voting record. Other candidates could hurt Rubio by attacking his past support for comprehensive immigration reform. Plus, there has been some chatter that Rubio isn't doing a particularly good job building a campaign operation, particularly in the early voting states. And even if Bush vanished from the race and Rubio picked up all his support, he'd still be trailing both Trump and Carson.

For Cruz, the main problem is, well, that the theory assumes Trump and Carson will vanish. That still could happen, and the history of non-politician candidates suggests it will — but the clock is ticking. Trump's ability to dominate headlines between debates, and the enthusiasm shown for Ben Carson on social media, could keep them around for some time. Cruz has spent years positioning himself to run against the Washington establishment, but his credentials as a political outsider are obviously inferior to theirs.

While watching this debate, though, it was easy to imagine both Cruz and Rubio rising above everyone else — and battling it out for the nomination in the end.