March 13 (Bloomberg) — In Maine, the insurer that has enrolled the most Obamacare customers isn't the state's well- established Blue Cross Blue Shield plan, owned by WellPoint Inc. It's WellPoint's only rival: Maine Community Health Options, a startup that didn't exist three years ago.

The newcomer, funded primarily by taxpayer money lent under the health care law, has won about 80 percent of the market so far in Maine's new insurance exchange, exceeding its own expectations, said Kevin Lewis, the chief executive officer.

Obamacare opponents predicted early on that insurance co-ops created by the law would fail, and that much of the $2.1 billion they were loaned to get started would be lost. Instead, the 23 co-ops that now exist nationally have enrolled about 300,000 people in health plans by combining low premiums with a certain homespun appeal, according to company executives.