Final answer:
Roosevelt's reasoning for supporting character as the most important quality of citizenship was because it represents an individual's ability to contribute positively to society with integrity and responsibility.
Step-by-step explanation:
Roosevelt believed that character is the most important quality of citizenship, as it underscores the individual's capacity to act with integrity and responsibility, contributing positively to the functioning and betterment of society.
His extensive public service, including his presidency, was marked by efforts to instill confidence in the American public, foster economic stability, and uphold just governance.
In his advocacy for the New Nationalism philosophy, Roosevelt contended that the government should balance ensuring human welfare with the protection of property, illustrating his belief that strong character in citizens leads to a more equitable and functional society.