For the first time ever, there's a real chance that Facebook and Google could be broken up.

It's going to be a tough, years-long battle. But the companies are facing existential legal threats as government regulators and state attorneys bring five separate antitrust cases against them: two against Facebook and three against Google.

None of the cases will be easy to prove. This is the most aggressive set of antitrust actions by the government in decades, and courts are more skeptical than ever. But the cases make a new era in antitrust enforcement, and anything is possible.

Protocol ranked the lawsuits in order of least to most likely to succeed.

4. Texas-led case against Google

Legal experts have expressed the most skepticism around the antitrust lawsuit against Google's ad stack dominance from the Texas-led coalition of 10 attorneys general. Some of the complaint's central claims, including alleged collusion between Facebook and Google, are enticing — but it's unclear if the coalition has the goods to back them up.

"The Texas case could be a killer case," said Chris Sagers, an antitrust professor at Cleveland-Marshall College of Law. If the states are able to prove a horizontal conspiracy between Google and Facebook to rig the ad tech market, it would amount to a clear violation of Section 1 of the Sherman Act, which prohibits agreements that restrict trade. But Sagers said it's all in the details, and the some of the allegations "seem more ambiguous and subject to interpretation."

It's difficult to analyze because so much of the complaint is redacted, particularly the sections about what Google admitted to in internal communications. And Google has already shot down a separate allegation in the suit, which claimed Google gained access to encrypted WhatsApp messages.

On the other hand, a court likely won't struggle with the concept that Google has outsized power over all levels of the ad stack, and there's significant public evidence that it engaged in plenty of manipulative behaviors to maintain that control.

It's also yet to be seen if any Democrats will join the Texas suit, which will struggle with credibility issues as Texas Attorney General Ken Paxton continues to face allegations of corruption and an ongoing FBI investigation.

3. Colorado- and Nebraska-led case against Google

The complaint from the coalition of 35 attorneys general led by Colorado and Nebraska is sweeping and ambitious, with sections detailing Google's exclusionary conduct in search, its efforts to limit the visibility of specialized search engines and its growing dominance in emerging technologies like voice assistants.

It's a serious case with broad bipartisan support, and its focus on Google's current efforts to muscle into voice assistants might appeal to a judge looking for ongoing anticompetitive behavior in a dynamic market. "Part of what I suspect these companies are going to argue is, 'What do you mean durable monopoly power? This is a dynamic setting and the moment you slow down, the rest of the world passes you by,'" said William Kovacic, former FTC chairman. "The Colorado complaint is saying, 'It is very competitive and you are using every bit of skill you have to anticipate what those new threats are and to squash them.'"

But it's an open question whether antitrust is the best mechanism to rein in self-preferencing, one of the central allegations of the Colorado case. Hal Singer, a managing director at antitrust firm Econ One, has argued that self-preferencing "does not fit into any well-received antitrust paradigm." And even if the laws could be "stretched" to accommodate this type of exclusion, the pace of antitrust litigation is likely far too slow to remedy the harms to innovation, he wrote.

It's yet to be seen how a court responds to allegations of self-preferencing as an antitrust violation. The states are arguing that Google restricts the way specialized sites like Yelp and Tripadvisor can advertise, harming their business and giving consumers fewer options.

The Nebraska and Colorado-led coalition is planning to consolidate its case with the DOJ's, and a judge will have to consider each allegation on its own.

"This lawsuit seeks to redesign search in ways that would deprive Americans of helpful information and hurt businesses' ability to connect directly with customers," Google said in a statement. "We look forward to making that case in court, while remaining focused on delivering a high-quality search experience for our users."

2. The FTC and state attorneys general bring cases against Facebook

The cases against Facebook from the coalition of 48 state attorneys general and the FTC read like a wish list from progressive antitrust activists. The FTC is calling for Facebook to spin off WhatsApp and Instagram while alleging the company has destroyed privacy protections and elbowed out potential competitors in the battle to maintain its position as the biggest social network in the world.

What's amazing about the twin cases is that the government could plausibly win, although it will be a steep uphill battle.

"You have a monopoly that is acquiring nascent competitive threats," said Maurice Stucke, a former DOJ prosecutor and professor of law at the University of Tennessee. "You have anticompetitive intent, anticompetitive design and internal documents to show how these acquisitions further that anticompetitive design."

The FTC and state cases are extremely similar and will likely be consolidated in federal court in Washington, D.C. They both focus on whether Facebook's acquisitions of Instagram and WhatsApp were anticompetitive and whether Facebook has leveraged the power of its APIs to kneecap potential rivals.

But the government will likely have to surmount deep skepticism of its market definition: "personal social networking." They'll have to work hard to prove that Facebook exists in its very own marketplace that excludes social media sites like TikTok and YouTube. "If I had shown up at a meeting and announced that Facebook didn't compete with Google, Apple or TikTok, I would have been laughed out of the room," wrote Matt Perault, formerly Facebook's director of public policy, in an op-ed on Thursday.

And the court will demand extensive evidence proving that Instagram and WhatsApp could have grown without Facebook's acquisition, a hypothetical situation that might be difficult to substantiate.

"Could Instagram have developed without the investment of money and know-how from Facebook?" said Kristen Limarzi, a partner at Gibson, Dunn & Crutcher and former DOJ antitrust official. "I think that's unclear, but that's what the FTC will have to prove."

1. DOJ's case against Google

The DOJ's case against Google, which was filed in October alongside a coalition of 11 Republican attorneys general, likely has the best shot at winning simply because it is the least ambitious.

The complaint hews as closely to the 1990s Microsoft case as possible — a case that the government won even though it did not ultimately result in Microsoft's breakup. Paralleling the Microsoft case, the DOJ's complaint narrowly targets Google's "exclusionary contracts" with other companies, most prominently its more than $12 billion deal to keep Google as Apple's default search engine.

So far, under the Trump administration, the case does not get into broader questions about Google's dominance in search or advertising technology. Legal experts said the DOJ's case alleges clear-cut violations of Section 2 of the Sherman Act, as long as it's able to substantiate its core claims.

"It's a plausible Section 2 argument that is pretty well-substantiated, with plausible reasoning and citations to what looks like real evidence," Sagers said.

Google has called the case "deeply flawed." "People use Google because they choose to, not because they're forced to," Google's chief legal officer, Kent Walker, said. But the DOJ will try to prove that users hardly have a choice in the matter.

The case could benefit from the well-resourced lawyers working against Google, including attorneys with Oracle, AT&T, Microsoft and other top firms, and the open-minded judge it's been assigned to, Amit Mehta.

It's still one of the most ambitious antitrust lawsuits to come from the U.S. government in decades, and it will face serious hurdles. Mehta could be skeptical of the DOJ's definition of the relevant market: "general search," which excludes specialized search engines like Amazon or Expedia. And it will be highly fact-specific, meaning the government has to provide extensive evidence proving its allegations.