By BARRY MASSEY and JERI CLAUSING Associated Press ALBUQUERQUE, N.M. (AP) -- Turnout was light across the state Tuesday as New Mexicans weighed in on the Republican presidential primary and narrowed their field of candidates for US Senate and Congress. Registered Republican voters could cast ballots for presidential candidates Ron Paul, Newt Gingrich, Rick Santorum or Mitt Romney, although Romney became the presumptive nominee last week with a win in Texas. Most eyes were on the Democrat primary, where US Rep. Martin Heinrich and state auditor Hector Balderas were competing in a gentlemanly race for the nomination to succeed retiring US Sen. Jeff Bingaman. Three veterans of the Albuquerque political scene were locked in a close and much feistier race for a shot at Heinrich's 1st Congressional District seat. With an Albuquerque Journal poll last month showing state Sen. Eric Griego and Bernalillo County Commissioner Michelle Lujan Grisham in a dead heat for the district, the candidates took an already nasty campaign to new levels. The two front-runners bombarded the airwaves and mailboxes in the campaign's final days with negative ads and mailings challenging each other's public and personal records. Former Albuquerque mayor Marty Chavez stayed out of the worst of the fray, focusing his final days on getting supporters out to vote. Balderas and Heinrich have kept their campaign polite, using a televised debate Sunday to agree on most key issues and instead attack the Republican front-runner, former US Rep. Heather Wilson. She is being challenged in the Republican Senate primary by Greg Sowards, a Las Cruces businessman. With Bingaman retiring after 30 years, the GOP is targeting New Mexico in its drive to capture control of the US Senate and return the battleground state to Republicans in the presidential election. In 2008, Democrat Tom Udall won the Senate seat of Wilson's mentor, Pete Domenici, a Republican power in Washington for three decades, giving Democrats control of both of the state's Senate seats for the first time in nearly 40 years. Wilson gave up her House seat to run in that race. She lost the GOP nomination to southern New Mexico congressman Steve Pearce after a national anti-tax group spent more than $600,000 on ads portraying her as too moderate on economic issues. Sowards levelled the same criticisms against Wilson for her voting record during a decade representing the 1st Congressional District. Wilson, an Air Force Academy graduate and Rhodes scholar, won a special election in 1998 to replace the late Republican Steve Schiff and then developed a reputation as a tough campaigner by repeatedly winning re-election in a swing district targeted by national Democrats. Heinrich, 40, is an engineer and former Albuquerque city councilor who won Wilson's seat after she stepped down. Among his proudest achievements since winning Wilson's House seat, he says, were saving 1,000 National Guard jobs at Kirtland Air Force Base and fighting for continued support for Los Alamos and Sandia national laboratories. Balderas, 38, was the underdog who positioned himself as a reformer. His grass-roots campaign focused on the fact that he had "lived the issues," having grown up in public housing and on food stamps in the northern New Mexico town of Wagon Mound, one of the state's smallest and poorest towns. In other congressional races, Rep. Ben Ray Lujan, the Democrat who represents northern New Mexico's 3rd Congressional District, is running unopposed. He will face the winner of the Republican primary between Frederick Newton and Jefferson Byrd. In southern New Mexico's 2nd Congressional District, Republican Rep. Steve Pearce is also unopposed. He will face Democratic challenger Evelyn Madrid Erhard in November.