LOCO HILLS, N.M. — At the diner she manages in the heart of New Mexico’s oil country, Joni Moorhead talks to roughnecks all day long about potholed roads, cramped lodging camps, soaring rents — and state politics.

“I’d load up my guns for the fighting if we could just secede and join Texas,” said Ms. Moorhead from Loco Hills, population about 125. “They love the money from our oil up in Santa Fe. But they treat us like dirt .”

Ms. Moorhead, 42, may sound more extreme than most. But go just about anywhere in southeastern New Mexico, the deeply conservative oil-rich region known as “Little Texas,” and people are seething over a political shift to the left i n the state capital.

A frenetic oil boom is laying bare this divide, while suddenly lifting one of the poorest states in the country into the top ranks of global oil producers. Normally that might be cause for celebration, but Democrats now in power in New Mexico are coming under fire on two fronts: from oil patch conservatives, for pushing to hike oil royalties and spend the windfall on progressive causes, and from environmentalists on the left, for allowing the oil boom to materialize in the first place.