Correction Appended

Two candidates are preparing to launch campaigns for New Mexico’s 1st district, and Democratic Rep. Martin Heinrich’s announcement that he’ll run for the open Senate seat is likely to lure several more to bid for his marginal district.

However, the Albuquerque-based district could become less competitive for Republicans under a new map being drawn by Democrats. The district needs to trim about 15,000 voters in redistricting, and Democrats, who control the state Legislature, want to slice off Torrance, a GOP-leaning county.

Torrance makes up about three-fourths of the district’s area size but is sparsely populated with just more than 16,000 people. Heinrich lost it by more than 1,000 votes in both of his Congressional elections.

There have been indications in recent elections that the 1st district is trending Democratic anyway. Heinrich won re-election in November by 4 points in a strong cycle for Republicans nationwide. President Barack Obama won the district in 2008 by a 21-point margin.

Still, the Democratic plan must be approved by Republican Gov. Susana Martinez. Unless Democrats in the Legislature are able to override her veto, the new Congressional district map would be destined to land in the courts. The uncertainty has both parties remaining optimistic about winning the seat.

Democrats have a deep bench of possible candidates. State Sen. Eric Griego launched an exploratory committee Friday — one day before Heinrich’s Senate announcement — and state Rep. Moe Maestas announced the following day he is weighing the race as well.

Beyond that, names being discussed include state Rep. Al Park, Bernalillo County Clerk Maggie Toulouse Oliver, Bernalillo County Commissioner Michelle Lujan Grisham (who lost to Heinrich in the 2008 primary for the seat) and Terry Brunner, the former chief of staff to Sen. Jeff Bingaman (D-N.M.).

On the Republican side, Albuquerque City Councilor Dan Lewis made his campaign official on Sunday. He is making the leap from the same position that Heinrich held before moving to Congress in 2008.

Lewis, a small-business man and pastor of a church, touted his accomplishments while serving in local government. New Mexico GOP insiders think that Lewis is shaping up as a real contender and that his fundraising numbers demonstrate early strength, even before he made his campaign official. Heinrich’s 2010 opponent, Jon Barela, hasn’t ruled out another bid.

The only other Republican seriously discussing a bid at this point is Janice Arnold-Jones, a former state Representative who finished a distant fifth in the 2010 gubernatorial primary. She has formed an exploratory committee and told Roll Call last month that she would decide by late May whether she can raise the money necessary to win.

Correction: April 5, 2011

A caption with a photo accompanying the article misidentified former Rep. Glenn Nye as Rep. Martin Heinrich.