Aetna wins important Florida approval, but Humana battle is far from over.

The Medicare-heavy state of Florida has given its blessing to Aetna’s $37 billion acquisition of Humana, on the condition that Aetna expands its health plan offerings in the state’s insurance exchanges.

Florida marks an important win for Aetna, given the several million Medicare Advantage and exchange beneficiaries the two insurers cover in the state. Several financial analysts believe the Florida approval bodes well for the transaction to get the thumbs-up from the U.S. Justice Department. But lawyers caution that not too much should be inferred from a single state insurance regulator.

“Remember Alf Landon and the saying, ‘As Maine goes, so goes the rest of the nation?’ But all he did was take Maine and Vermont,” said David Balto, referring to the former 1936 Republican presidential nominee who won a supposed bellwether state, but was ultimately crushed in the general election by Democrat Franklin Delano Roosevelt.

“The Justice Department is appropriately the last word when it comes to this merger,” said Balto, a former antitrust attorney for the Department of Justice and the Federal Trade Commission. He heads the Coalition to Protect Patient Choice, a group that has actively opposed the recent spate of health insurance mergers.

The Florida Office of Insurance Regulation approved the Aetna-Humana deal Monday after mulling over its merits for several months. A consent order (PDF)imposed several conditions pending federal approval. Most notably, Aetna will have to sell exchange plans in five more Florida counties by 2018, a concessionthat would force the Hartford, Conn.-based insurer to stay committed to the Affordable Care Act’s exchanges, even though it has voiced some displeasure.

However, the state required no divestitures. Most experts, and even Aetna CEO Mark Bertolini, expect the insurer will have to sell some overlapping plans to alleviate federal anticompetitive concerns.

Florida regulators stipulated other conditions, including a three-year requirement to document the efficiencies of the new combined company, and a guarantee that Aetna’s coverage policies for HIV/AIDS drugs will extend to all Humana plans.

A key finding in Florida’s consent order is the interpretation that Medicare Advantage competes directly with traditional Medicare. The state upholds Aetna’s core argument that the combined company will cover only 8% of all Medicare beneficiaries, most of whom are still enrolled in the traditional program. Florida’s insurance commissioner also backed Aetna’s case that Medicare Advantage enrollees always have the option of jumping to traditional Medicare during the annual enrollment period.

However, a Health Affairs study from October found that many of the people who switch from Medicare Advantage to traditional Medicare are sicker on average, which researchers said “raises questions about the role of Medicare Advantage plans in serving high-cost patients with complex care needs.”

Jeff Miles, an antitrust attorney at Ober Kaler, believes Florida’s approval is “only marginally positive at best” for Aetna. The federal government is taking a much closer look at how traditional Medicare competes with Medicare Advantage, how geographic markets are defined, how difficult it would be for companies to enter Aetna’s markets, and whether overlap problems can be sufficiently solved by divestitures.

“This is one insurance department among many,” Miles said.

Aetna has obtained 10 of 20 necessary state approvals, the insurer said in a statement. Many legal experts have noted the important roles that state insurance commissioners play in mergers, but Balto said he believes the deal still faces an extreme degree of uncertainty from the Department of Justice.

“The weather in Miami does not tell you at all what the weather will be in Washington, D.C.,” he said.