Yes. It can be assumed that Sumner had the support of the people as the legislature was popularly elected. The legislature also passed Sumner's own Objections to the Mexican War. This appears to be another sign that he was respected and had the support of the voters of Massachusetts.
B. Because even with many issues that plagued the Roman Empire economically and politically, By the later years of the empire the Roman military was mainly comprised of trained Barbarian soliders who were inferior to earlier Roman soliders causing a significant decrease in the Roman Empires's Military capablities so many barbarian tribes that began to grow such as the Huns, Vandals, Goth etc. Put immense pressure on the Empire, driving them into the ground economically and causing many issues within the government and eventually being sacked, thus marking the end of the Roman Empire. Sorry for the wall of text but hope this helped :)
The absolutists governments in europe tend to believe in Sovereignty, in which there will be a person or a group that held the power that could be considered above laws that couldn't even be remotely apprehended by its people.
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