Nthe early 1800s, how was the belief in manifest destiny most likely to affect the admission of new states into the union? the belief in manifest destiny meant that slavery was likely to spread to all the territories as they became new states. the belief in manifest destiny meant that european nations were likely to give up their claims to territories to avoid a battle over slavery. the belief in manifest destiny meant that the united states was destined to outlaw slavery in all new states. the belief in manifest destiny meant that the balance between free and slave states could shift as the united states expanded to the pacific coast.