Momentum in Senate the race in New Mexico between Rep. Martin Heinrich (D-N.M.) and former Republican congresswoman Heather Wilson has swung to and fro, but lately, there are have been some emerging signs that Heinrich has the upper hand.

After a review of the most important factors in the race, The Fix has moved the New Mexico Senate race out of the tossup category and into the collection of races that leans toward the Democrats.

The first reason for the move is money. A strategist tracking ad buys in the state confirms that the National Republican Senatorial Committee has pulled its $2.3 million fall TV ad reserve, a sign that its confidence in the pick-up opportunity has faded.

The second positive indicator for Heinrich: His own polling shows that as of the middle of this month, he held a slight lead over Wilson. Republican-leaning automated pollster Rasmussen Reports also shows Heinrich with a slight lead in the race, as does a Democratic poll conducted for a coalition supporting the congressman.

That coalition, comprised of environmental and conservation groups, has spent just under $1 million on TV ads to help Heinrich's candidacy. The coalition largely supports Heinrich because of his record on public lands and public health issues.

The environmental coalition money has been an effective buffer for Heinrich against Republican groups targeting him. The GOP-aligned groups American Crossroads and Crossroads GPS have spent about $850,000 on TV ads in the race so far, meaning that the environmental groups' dollars have roughly matched the Crossroads money.

Navin Nayak, a spokesman for the League of Conservation Voters, which belongs to the coalition, said the effort on behalf of Heinrich is unprecedented. "We've never done this in a Senate race before," he said.

The momentum has swung away from Wilson, but the race is not completely beyond her grasp. Earlier in the race, she showed positive signs that caught the attention of national Republicans. She outraised Heinrich during the first two quarters of the year, and didn't have any trouble advancing from what was once viewed as a potentially tough primary. For a Republican, her moderate profile is a good fit for the Democratic-leaning state.

For now though, Heinrich has shown an ability to withstand Republican attacks and scare away some national Republican money. That's good news for Democrats who are trying to maintain their Senate majority in November.