The market often works in mysterious ways, then it can turn into the wild west when it comes to raw speculation. It turns out that speculators love guessing about mergers. Now we are in a sort of speculation soup about which of the health insurance providers are going to merge.

24/7 Wall St. cannot help but wonder if it is possible that one of these top companies could be left without a merger partner. Mergers among insurance providers are an unintended consequence of the Affordable Care Act. It seems as though the insurance giants have figured out that the only way they can shield themselves from unlimited liability is to make sure that they have so many insured people as members that they simply cannot fail. With all the merger speculation in health care insurance right now, is it possible that one player, or even two players, could be left out in the cold when it comes to mergers?

Anthem Inc. (NYSE: ANTM) is reportedly the one that approached Cigna Corp. (NYSE: CI) about a merger. Anthem is also one of the companies that was speculated about as one of the parties interested in Humana Inc. (NYSE: HUM) as well. And on Tuesday came word that UnitedHealth Group Inc. (NYSE: UNH) is now interested in acquiring Aetna Inc. (NYSE: AET). And UnitedHealth is big enough to acquire any company in the field. The reality is that any of the larger companies could try to make a grab for the smaller insurance giants.

If you didn’t know any better about the industry, it almost sounds like an insurance orgy. It isn’t. It is how these companies are planning to survive under the Affordable Care Act. As a reminder, insurance companies were the most targeted sector of health care under Obamacare. The end result sure looks as if none of the players want to be left out. You could literally be looking at an insurance sector that is down to three or so major carriers in each market ahead.

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Anthem operates as a licensee of Blue Cross and Blue Shield and served 37.5 million medical members at the end of 2014. Its market cap is $44 billion. Anthem shares were up 1.5% at $166.98 late on Tuesday. Its 52-week range is $105.02 to $170.98, and the consensus analyst price target is $171.65.

Aetna counts some 46 million people as its customers in various aspects of health business lines. Its market cap is $43.6 billion. Aetna shares were up 3.3% to $124.98, against a 52-week range of $71.81 to $128.65 and against a consensus analyst target of $124.31. Aetna shares were around $115 to start this week.

Cigna has a $39 billion market cap. A recent press release shows that Cigna operates in 30 countries and jurisdictions, and represented that it has over 88 million customer relationships throughout the world. Cigna shares were up 0.2% at $153.73, versus a 52-week range of $85.75 to $164.00 and a consensus price target of $146.71. This was a $137 stock in recent days before merger interest rumors broke.

Humana has a $30 billion market cap. As of March 31, 2015, the company had about 14.2 million members in medical benefit plans and about 7.4 million members in specialty products. Humana was not showing much on Tuesday, with shares down 2.8% at $200.81. Its 52-week range is $115.51 to $219.79, and its consensus price target is $190.06. In late May, Humana shares jumped to $214 from $178 on merger speculation.

UnitedHealth, a Dow Jones Industrial Average stock, has a market cap of $115 billion and is the largest of its peers. UnitedHealth shares were up 2.2% to $121.60, against a 52-week range of $77.53 to $123.76 and a consensus price target of $138.80.

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As a reminder, these stocks have all outperformed the market this year. In fact, UnitedHealth is up the least, with a gain of about 19%. Aetna and Anthem both are up over 30%, and Humana and Cigna are up over 40% so far this year. Speculators will speculate, and some days the prior favorite gets treated like the dog. And the prior day’s ugly duckling sometimes gets treated like the next queen.

It is of course possible that one of these companies could get left out of the insurance M&A shell game to fend for itself. That being said, these health insurance giants are all big winners this year — even if one day may have differing reactions.

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