So far, Ross is the only Democratic challenger (and the only gay one, to my knowledge) of Patrick, although the Green Party is running its own candidate, Jill Stein. As of now, it is unclear why Ross is choosing to run as a Democrat instead of as a Green or independent, other than the answer of having an organizational structure behind her. On the blog Blue Mass Group, before she decided whether she was going to run or not, she wrote:
If I run as a Democrat, that would allow me to combat the broken structure, with the help of the many folks already in state government who are dedicated to serving the people. Many Democratic friends have urged me to throw my hat in the ring, but so have my Republican, Green and unenrolled friends. The decision I and my team make will be based on how I can best serve all of the people of the Commonwealth.
When running as a Green, Ross only received a bit less than two percent of the vote. This would make her seem completely non-competitive. However, the difference this time is obviously that she's running as a Democrat. And if she makes it onto the ballot - which would take 15% of the delegates at the state Democratic convention and something like 10,000 signatures - which is not unlikely, then she is running in a completely different race than 2006.
Interestingly, Ross announced her candidacy at an AFL-CIO conference:
Ross's announcement came after Patrick pulled out of the state's AFL-CIO conference in Plymouth. Patrick, who was invited by the AFL-CIO, backed out after police unions picketed the event and other unions said they would leave upon his arrival and join the police unions in demonstrating.
As for her platform, it's not entirely clear yet. However, the Boston Globe writes:
Ross said during the 2006 campaign, among other things, that she was running for governor to be a voice for the poor, and she wanted a structural change in the tax system, which she believed heavily favored the wealthy.
One of her first acts as governor, she said, would be to push for a new "circuit-breaker" tax break to help low- and moderate-income residents, a move that would shift more of the tax burden onto the wealthy. Ross also wanted corporations to pay taxes based on the amount of business they do in Massachusetts rather than on the facilities they have here.
Ross also called for devoting about $50 million in state money to low- and no-interest loans for small businesses, municipalities, and property owners who want to add solar panels or wind turbines. She said the initiative would nurture the state's alternative-energy industry, reduce demand on the power grid, and lower energy costs for cities and towns.