Answer:
The concept inadvertently challenged by Progressives' call for expert opinions was:
Elected officials' autonomy
Step-by-step explanation:
Through the efforts of the Muckrakers or progressive journalist, the corruption of the established institutions and leaders were exposed. Elected officials because they were wallowing in corruption did not want their administrations probed by non-elected bodies, sought vicariously for autonomy. They wanted the checks and balances through independent judiciary to be removed. However, during the 1890s to 1920s, an era known as the Progressives Era, the progressives challenged the existing autonomy of elected officials, proposing to end the monumental corruption that was in vogue at that time.