But when a long train of abuses and usurpations, pursuing invariably the same object evinces a design to reduce them under absolute despotism, it is their right, it is their duty, to throw off such government, and to provide new guards for their future security. ~the declaration of independence despotism means an oppressive dictatorship. usurpations means taking over something by force or oppression. given this information, according to this excerpt, what condition is sufficient cause for people to form a new government?

Constant oppression of the citizens by the government.

This excerpt of the Declaration of Independence tells us what the Founding Fathers believed to be reason enough for the citizens to form a new government. Here, they argue that "a long train of abuses and usurpations" is necessary, which means that abuses from the government have to be constant, as opposed to an anomaly. Moreover, the actions must be designed to "reduce them under absolute despotism." In this case, they argue, the citizens have a duty to change the government and protect their future security.

verifying the answer of @ Holesstanham

checked answer on my test, and it is correct!