The muckrakers of the Progressive Era paved the way for political reforms by alerting people to conditions that, in the muckrakers’ eyes, needed fixing. This made the people put pressure on the government for reforms.
In our democratic system, things do not tend to change unless the people do not like the status quo. If one group thinks something is a problem, but no one else is paying attention, the problem will probably not get addressed. Therefore, if you think something is a problem, you need to publicize it so that everyone else will think it is a problem as well. This is what the muckrakers did. Jacob Riis made people aware of the terrible conditions in which poor immigrants lived. Upton Sinclair made people aware of what the slaughterhouses were like. Other muckrakers exposed problems like the monopoly of Standard Oil. By making people aware of these problems, they allowed the people to put pressure on the government, thus paving the way for political reforms.