ST. PAUL -- One in five Minnesotans are expected to buy health insurance offered by a mostly online marketplace that a newly written bill would establish.

The marketplace, known as a health care exchange, is required by federal law known as Obamacare and must be in place by Oct. 31.

"A Minnesota-based exchange allows Minnesota the opportunity to modernize our public systems," state Sen. Tony Lourey, DFL-Kerrick, said.

The bill Lourey and Rep. Joe Atkins, DFL-Inver Grove Heights, unveiled Wednesday would establish a seven-member public-private board to govern the insurance sales effort that would serve 1.1 million Minnesotans. If the state does not take action, the federal government will set up its own insurance exchange.

The measure would require the state to withhold 3.5 percent of insurance premiums collected from policy sales to fund administration. With that, Lourey and Atkins said, no funds should be needed from state tax money.

Three Republican lawmakers appeared with bill supporters, including five Dayton administration commissioners, at a news conference. They did not promise the GOP was on board and bill backers said the measure needs to build support, especially among businesses.

"There still is a little bit of resistance here and there," Lourey said.

"I think it's a big mistake," Minority Leader Sen. David Hann, R-Eden Prairie, said of Minnesota's participation. "I don't think we should be doing it."

Other Republicans said they will work with Democratic bill authors.

"It's something we have to do in a very short, fast fashion," Sen. Julie Rosen, R-Fairmont, said.

The bill must pass by March 22 for the exchange to begin Oct. 31, Lourey said.

The proposal discussed Wednesday is one of several bills expected to be debated to bring Minnesota into compliance with Obamacare. Lourey said another one probably will be to move low-income Minnesotans in the state-subsidized MinnesotaCare insurance program into the exchange.

"We intend this to be a starting place," Lourey said of the Wednesday bill.

Obamacare is historic, Rep. Tom Huntley, DFL-Duluth, said. He said it was the most important move in health insurance since Medicare and Medicaid were created in 1965.

While all Minnesotans will have access to the exchange, the same plans may not be available statewide.

People who do not want to use computers would have access to insurance purchasing over the telephone or some in-person locations.