Heinrich, who represents New Mexico's 1st Congressional District, is vying for the Senate seat held by retiring Sen. Jeff Bingaman, also a Democrat.
Luján is running for reelection as the representative for the 3rd Congressional District, which includes San Juan County and parts of the Navajo Nation.
The tribe's speaker sent letters to both Democrats expressing the Navajo Nation's support for their campaigns.
The two politicians showed up at Democratic Party Headquarters in Farmington earlier this month to greet local supporters, and to talk about issues important to residents such as jobs, energy and the environment.
Heinrich has vowed to lower taxes on the middle class, cut the national debt, and protect the recently passed federal health care law.
Luján has similar goals, and also plans to work for energy independence, improving schools, and helping the state's veterans via recent health care reforms.
Heinrich is running against former Republican U.S. Rep. Heather Wilson, who represented the 1st Congressional District from 1998 to 2009.
She was the first female military veteran elected to a full term in Congress. As such, she focused on national security issues, as well as health care and energy.
Luján is running against Jefferson Byrd, a Republican businessman and ranch owner from Tucumcari.
Byrd identifies himself not as a politician, but as a father and husband concerned about the direction of the country.
The Navajo Nation historically has endorsed Democratic candidates in both state and national elections. The tribe this year has not endorsed a presidential candidate.