The proposed merger between Tufts Health Plan and Harvard Pilgrim Health Care would create a sizable new health insurer to compete with market giant Blue Cross Blue Shield. Now, state officials are evaluating if that would help or hurt the state's health consumers.

"The Baker-Polito Administration believes that any merger of healthcare companies should result in greater transparency, lower prices and better outcomes for patients," Gov. Charlie Baker's spokesman Brendan Moss said in a statement.

If Attorney General Maura Healey's office approves the merger, Baker's Division of Insurance will then review the transaction to assure no disruptions in health care coverage or access. Baker was Harvard Pilgrim's CEO from 1999 to 2008.

Read more: Harvard Pilgrim, Tufts Health Plan Announce Merger

Secretary of State William Galvin told WGBH News the most important thing for state watchdogs to do now is to scrutinize the outcomes of a merger for consumers and health providers.

"I think the most important thing is that there be sufficient scrutiny of this entire process," Galvin said. "This is not simply a merger of two private companies that have nothing to do with anything. It's a very critical part of our health care system for many people."

The surprise merger, if approved by the myriad federal and state officials, will recast medical coverage for 2.4 million customers in Massachusetts, Maine, New Hampshire, Rhode Island and Connecticut. It would also establish a direct competitor for Blue Cross Blue Shield, the region's leading insurer, at a time when employers and state government leaders are trying to lower the cost of health coverage.

"It starts with, What does it mean to patients? What does it mean to the insured here? That's the number one question. And what does it mean to the institutions that provide the services," Galvin said.

Healey's staff is in contact with Tufts and Harvard Pilgrim about their plans. As the lead regulator of nonprofits, it will be Healey's responsibility to rule if the merger serves the public good and complies with anti-trust laws.

"Our office has been in touch with both parties and will review the proposed transaction as more information becomes available," Healey spokeswoman Meggie Quackenbush said in an emailed statement.

This much is certain: State officials agree that the announced merger could significantly shake up the Massachusetts health care market.

The state's health care cost watchdog, the Health Policy Commission, doesn't have any jurisdiction over a merger between health insurers, but a spokesman for the commission said the merger could have a significant impact on the Massachusetts health care market.

“While details are still in development, the potential merger of Harvard Pilgrim Health Care and Tufts Health Plan, two of the largest health plans in the Commonwealth, could have a significant impact on the Massachusetts health care market. We look forward to learning more as discussions between the parties progress," HPC spokesman Matthew Kitsos wrote.

Amy Rosenthal, the executive director of the Massachusetts advocacy group Health Care For All, said they will watch carefully to see how the merger will impact consumers.

"Health Care for All will closely monitor the proposed merger to better understand whether the anticipated efficiencies will actually translate to lower costs for consumers, broader networks and an increase in community investments," Rosenthal said. "We'll also want to ensure that consumers are able to continue to see their providers and that Connector and MassHealth plans continue to be available as these changes unfold."

Jonathan Gruber, a health care economist at the Massachusetts Institute of Technology who was an architect of the Affordable Care Act, said that it is possible the merger could reduce consumer costs, though that is not always the case.

"It certainly is plausible that between the cost savings and a negotiating power improvement they could deliver lower health care prices through this merger," Gruber said. "I'm just saying in practice that's rarely worked out in the past. And at some point we have to draw a line because these mergers are just not working to the benefit of the consumer."

This article has been updated to attribute the quote "It certainly is plausible ... benefit of the consumer." to Jonathan Gruber, not Amy Rosenthal.

WGBH News' Mark Herz contributed to this report.