- The main concern was that annexing Texas would upset the balance of power in the Senate between free and slave states
- If Texas was annexed, it would add two more slave states to the Union
- Some Northerners worried that the admission of Texas would increase the political power of Southerners.
Fears of war with Mexico
- Annexing Texas could lead to war with Mexico to which Texas still belonged
- Mexico had warned that annexation would result in war
Financial burden
- The US would have to take on Texas's $10 million debt if it was annexed
Texas as a potential threat to Native Americans
- Some Americans worried that annexing Texas might lead to conflicts with Native American tribes living in the region