Democratic candidates vie for votes of New Mexico's 3 major constituencies

Scant attention will fall on New Mexico next Tuesday as California and New Jersey tally their delegate-showering results in Democratic primaries. But the contest there - for 23 of the state's 28 delegates - is at least as closely fought.

New Mexico should probably be considered Gary Hart country, since he is otherwise undefeated in the Rocky Mountain West, and the state shares a long border with the senator's home state of Colorado. But New Mexico does not follow the Rocky Mountain pattern.

For years, the political equation in New Mexico was north vs. south. Now it has become a three-way equation: the ''Hispano'' north, ''Little Texas'' in the south, and young newcomers in Albuquerque - each with roughly a third of the state's voting population.

They add up in a way that makes the primary too close to call.

New Mexico's Hispanos are not Mexican-American. Rather they descend from 17 th-century Spanish settlers who pre-date both the Mexican and American republics. They learned politics electing officers for their local acequias (irrigation ditches) under Spanish government, and have been active ever since.

The Hispanos are mostly rural, subsistence farmers and ranchers, ''very elderly, very (Roman) Catholic, very traditional and conservative in their personal views,'' says Chris Garcia, a political science professor at the University of New Mexico and president of the state's major polling firm, Zia Research.

''It's pretty obvious to me that Walter Mondale will come out ahead (among Hispanos), but he may not be way ahead,'' says Dr. Garcia.

Hispanos actually turn out to vote at higher rates than the state's Anglos. So in a close race with low voter turnout - which is the forecast in New Mexico - this group becomes very important.

Nowhere is turnout likely to be lower than in ''Little Texas'' in the southeastern part of the state. This is oil and gas country with vast ranches, just like west Texas. These are conservative, independent Democrats, and it is no secret that they will be voting for Ronald Reagan in November.

Hart campaigners are hoping to do well in Little Texas, while Mondale people say Hart is seen there as young, inexperienced, and liberal on foreign policy.

The emerging third leg of the New Mexico equation is the Albuquerque area. Hart is thought to have the edge there. The low part of the city, next to the Rio Grande on the west, is mostly Hispanic, and mostly backing Mondale. But as the altitude increases toward the Sangre de Cristo foothills to the east, Hart gains favor. Albuquerque is a fast-growing city of young newcomers, a prime Hart constituency.