Question

Why didn't President Van Buren want to annex Texas?​

Answer 1

Martin van Buren refrained from annexing Texas after the Mexicans threatened war.

Answer 2

Inclined more and more to oppose the expansion of slavery, Van Buren blocked the annexation of Texas because it assuredly would add to slave territory–and it might bring war with Mexico. Defeated by the Whigs in 1840 for reelection, he was an unsuccessful candidate for President on the Free Soil ticket in 1848.