So, is he saying he doesn't recognize the Treaty of Guadalupe-Hidalgo?
What matters to him the most is the political expediency of the moment.
The population of New Mexico Territory in 1850 was 61,547 (including what is now Arizona). I believe that figure excludes "Indians not taxed." Probably all but a small fraction of that 61,547 were already there when New Mexico still belonged to Mexico--but most of them probably were there before 1821 and may have been more "Spanish" than "Mexican."
New Mexico is said to be 43% "Hispanic," but what percentage of that is descended from the people living there in 1848, and what percentage from later immigrants from Mexico, I don't know. New Mexico's population has approximately doubled in the past 40 years, while the US population has grown just over 50%.