The race for New Mexico’s open 1st district has gone nuclear.

The two leading candidates in Tuesday’s Democratic primary launched blistering ads against each other in the past two days, a final negative turn in a three-way race that always had the potential to get ugly.

It’s been a true horse race so far, with the three candidates — state Sen. Eric Griego, Bernalillo County Commissioner Michelle Lujan Grisham and former Albuquerque Mayor Marty Chavez — moving ahead or falling behind over the past few months. The winner will be heavily favored to hold the Albuquerque-based seat of Rep. Martin Heinrich (D), who is running for Senate.

Chavez began the race with the highest name recognition and as the favorite, but all public and private polling in the past week has found Griego and Lujan Grisham neck-and-neck for the lead. That’s led the two to attack each other over the airwaves, both targeting the others’ records on one issue or another.

Griego and Lujan Grisham released polls last week that found them both in the low 30s, with Chavez polling in the 20s. An independent poll conducted for the Albuquerque Journal and released Sunday found Griego and Lujan Grisham tied at 33 percent, with Chavez at 20 percent and 14 percent undecided.

“The two frontrunners were in a virtual tie in our recent poll. Now they are barraging each other with attack ads,” said Brian Sanderoff of Research & Polling Inc., which conducted the newspaper poll. “It will be interesting to see whether this helps Marty Chavez, who lagged behind the frontrunners in the poll. This race is too close to call.”

Progressive Kick, a super PAC supporting Griego, set the ad war in motion by hitting Lujan Grisham for her record overseeing a state-run nursing home as state secretary of Health. The Lujan Grisham campaign called the attack “false” and responded with a hit of its own against Griego.

Lujan Grisham ran with a story that broke last week detailing 11 arrest warrants issued against Griego for various traffic violations. The ad got New Mexico political circles buzzing about whether that was the right move for a candidate tied for the lead.

“These three-way races, it’s not an automatic that you can nuke, because you have the third candidate in play,” said Joe Monahan, a New Mexico political analyst and blogger. “Once nuclear missiles are fired, you have the retaliatory launch.”

Griego fired back at Lujan Grisham on Wednesday with a TV ad that featured themes similar to the super PAC ad.

“Eric Griego has taken full responsibility for his traffic tickets,” Griego campaign manager Ed Yoon said. “But in light of her personal attacks, we think it’s time voters heard the truth about her record when she was in charge of New Mexico nursing homes.”

It was always assumed that the frontrunners heading into the homestretch would be Chavez and Griego. But Lujan Grisham, who was endorsed by EMILY’s List, hit the airwaves first with an ad highlighting her work on behalf of seniors, followed soon after by Griego, who has the support of national liberal organizations and labor unions.

“We made a conscientious decision to be the first on TV, and we were,” Lujan Grisham spokesman Gilbert Gallegos said. “And I think we stayed a step ahead throughout.”

Despite plenty of earned media for his clever ads, Chavez, who is backed by President Bill Clinton and is seen as the most moderate of the three, didn’t spend big on TV until this week. An ad running now features Chavez getting punched in the gut by a professional boxer in the corner of a boxing ring.

The Chavez campaign said its plan all along was to come in with a late media push. But he’s trailing his opponents, and the question remains whether the campaign should have been on the air to combat negative headlines about his relationship with Loretta Mares, a former city contractor charged with fraud.

However, Chavez is not the target of negative ads in the final week, a development his campaign does not mind.

“Voters are really learning about the records of our opponents right now, and that’s important,” Chavez campaign manager Alan Packman said. “Marty’s record is an open book. Anything that’s good or bad that you want to say about Marty has been said. People are just learning about Eric Griego and Michelle Lujan Grisham now.”

Griego has raised $851,000 for the campaign, about $200,000 more than his two opponents. But he ended the pre-primary fundraising period on May 16 with just $87,000 on hand. Lujan Grisham had $122,000 left to spend and Chavez had $168,000 still stashed away for his late push.

Monahan said the campaign is finishing in a negative phase, and the only surprising result would be if Chavez overcame his lag in the polls.

“You know this is the pivotal moment,” Monahan said. “You just don’t know which way for sure it’s going to turn out.”