It may not be a presidential swing state this year, but New Mexico is at the heart of the fight for the Senate.

Recent polling, fundraising and third-party spending reports illustrate just how competitive the race between Rep. Martin Heinrich (D) and former Rep. Heather Wilson (R) is less than four months out.

After the second fundraising quarter, Heinrich had a slight edge over Wilson in both cash on hand and polling. Democrats expect the state’s demographics and a victory for President Barack Obama to put Heinrich over the top come November, but the race remains too close to call.

“Martin Heinrich holds an early lead against Heather Wilson,” independent New Mexico pollster Brian Sanderoff said. “However, it’s too early to predict the outcome of the race. In all likelihood the race will narrow.”

The two candidates have represented the Albuquerque-based 1st district for the past 14 years combined. In interviews with Roll Call, each claimed a proven record of Hispanic support and a message better suited to the broad electorate.

In an increase of nearly 25 percent since 2000, Hispanics now make up 46 percent of New Mexico’s population, by far the highest of any state in the country, according to 2010 census figures. This demographic accounted for 41 percent of the state’s 2008 electorate.

“I think if you look at past polling data, you’ll see that I’ve consistently received better numbers with Hispanics than a Republican needs to win statewide,” Wilson said in a telephone interview Monday. She reiterated that point in a Wednesday briefing with reporters at the National Republican Senatorial Committee.

At a coffee shop a few blocks from the Capitol last week, an hour after voting against a repeal of Obama’s health care law, Heinrich said he had won about two-thirds of the Hispanic vote in past elections, which would be more than enough for a Democrat to win statewide.

“People call it a lean-blue state,” said Heinrich, who succeeded Wilson in 2008, when she retired to run for Senate. “When you’re north of 60 percent with Hispanic voters and you’re doing well with Anglo Democrats as well, it is a lean-blue state. But you have to have that turnout.”

Obama visited New Mexico in March, and unlike some of his fellow Democratic Senate candidates, Heinrich hopes the president swings by again as the elections near. The president stopped in Albuquerque’s South Valley about a month before the 2010 midterm elections, which the Congressman survived despite a national Republican wave.

Wilson needs  presumptive GOP presidential nominee Mitt Romney to keep the margin smaller than in 2008, when Obama won the state by 15 points. But if the presidential contest doesn’t get more competitive, Heinrich conceded that his campaign will likely need to pick up the slack on field operations, a vital program to turn out Hispanic voters.

He will also lack the assistance of a straight-ticket device option, which allowed New Mexico voters to choose a party’s entire slate of candidates with a single selection but is not an option for the first time in decades.

Wilson consultant Todd Harris said at Wednesday’s NRSC briefing that her “path to victory is going to be to obviously hold the Republican base, but also to add to that coalition with a significant chunk of independents and conservative Democrats, some of whom may be voting for” Obama.

New Mexico’s Senate seats were once a bastion of stability, but in the past four years the state will have lost 66 years of Senate tenure. Democratic Sen. Jeff Bingaman is retiring after 30 years, following Republican Pete Domenici’s retirement in 2008.

“Vacant Senate seats are a rarity in New Mexico,” Sanderoff said. “Given the power of incumbency, everyone knows that the winner of this vacant seat will probably hold it for a very long time, thus massive resources will be expended on influencing the outcome of the election.”

Heinrich is backed by a coalition of environmental and conservation groups that have pledged $1 million in support on the airwaves so far, likely providing him the largest outside support for a Democratic Senate candidate in the country. He needs it. He has an imposing opponent — one of the GOP’s top recruits — and millions in outside spending against him yet to come.

While the state has trended Democratic in recent federal elections, Republicans could be encouraged by Gov. Susana Martinez’s victory in 2010. She has governed as a pragmatic but unabashed conservative since taking office last year.

Heinrich has been the target of GOP-aligned groups since the June 5 primaries, plus two positive ads on Wilson’s behalf by American Crossroads — the only two positive Senate ads the group has aired all cycle. The U.S. Chamber of Commerce also just launched a positive ad on Wilson’s behalf.

The Heinrich campaign estimates that spending by outside groups has been about even since the primaries, with each side spending about $650,000 on Wilson and the Congressman, respectively, as of last week. Heinrich was criticized in an ad last month by the American Future Fund on federal spending, while American Commitment, another GOP-aligned group, slammed him on taxes.

The environmental groups working on Heinrich’s behalf include the Defenders of Wildlife, League of Conservation Voters, NRDC Action Fund, Sierra Club and Environment New Mexico. They’ve launched TV and mail campaigns accusing Wilson of supporting corporate polluters.

“There’s already been a lot of money spent in this race, and I don’t see the numbers moving at all, one way or the other,” Heinrich said last week. “We’ll be up on television soon, and we’ll stay up through November.”

His campaign launched its first general election television ad on Tuesday, showing him working in the community and highlighting his connection with middle-class voters.

Wilson outraised Heinrich in the second quarter, $1.6 million to $1.4 million, when Heinrich had a competitive primary. Heinrich still ended the quarter with slightly more cash, with almost $1.8 million in the bank compared with more than $1.6 million for Wilson.

A poll conducted for environmental groups from June 28 to July 1 by Democratic firm FM3 found Heinrich ahead 49 percent to 45 percent. That’s nearly identical to internal polling conducted for Heinrich’s campaign, which had him up 50 percent to 45 percent, he said. Wilson pollster Glen Bolger said Wednesday that the campaign’s latest internal poll from last month had Heinrich up 48 percent to 45 percent.

Heinrich is counting on the support of the state’s two Democratic Senators, Bingaman and Tom Udall. They headlined a fundraiser for him earlier this month, and Bingaman has told Heinrich he’ll help as much as possible. His primary opponent, state Auditor Hector Balderas, has also been helpful, Heinrich said.

Martinez, a longtime friend of Wilson’s, was recently the special guest for an event in Las Cruces, and the campaign will welcome Sen. Orrin Hatch (R-Utah) to the state on Saturday.