Which president believed that residents of New Mexico would favor joining Texas?

The president who believed that residents of New Mexico would favor joining Texas is indeed Mirabeau Lamar. Lamar served as the second president of the Republic of Texas and is known for his expansionist views and desire to promote the idea of Texas’ territory extending further southwest. He envisioned that residents in New Mexico might have cultural and economic ties to Texas, and he anticipated that they would support annexation due to these shared interests.

At that time, many leaders in Texas were motivated by the idea of expansion and the potential for growth, which was a significant theme in the early history of Texas. Lamar’s belief in the annexation of New Mexico reflects the mindset of some Texas leaders who viewed the region as ripe for incorporation into Texas, often influenced by notions of Manifest Destiny, which suggested that the United States was destined to expand across the continent. This idea was common among several political figures in the 19th century, but it was particularly characteristic of Lamar's presidency and policies.