Final answer:
The argument presented in Source 1 is that the process used to elect the senate during the progressive era has led to it looking out for wealthy interests.
Step-by-step explanation:
The Progressive Era in the United States was a period of social, political, and economic reform that took place roughly from the 1890s to the 1920s. It was characterized by a widespread desire to address the social and economic challenges arising from industrialization and urbanization during the late 19th and early 20th centuries. Progressives sought to improve living conditions, eliminate corruption, and address the inequalities and injustices brought about by rapid industrial and social changes.
The argument presented in Source 1 is that the process used to elect the senate during the progressive era has led to it looking out for wealthy interests. This argument is in line with the goals of the muckrakers, who exposed corruption and advocated for social justice during this time.