Final answer:
Progressives like Teddy Roosevelt and Bernie Sanders have historically challenged the political establishment, advocating for reforms such as workers' rights and economic equality. Their movements lead to changes within political parties, influencing policies and sometimes causing party realignments.
Step-by-step explanation:
Historically, progressives have played a significant role in challenging the political establishment and pushing for reforms. In the early 20th century, figures like Teddy Roosevelt emerged as leaders advocating for change. They wanted to make the government more responsive to people's needs, combat the power of party bosses, and end corruption. Roosevelt's Progressive policies included promoting an eight-hour workday and women's suffrage, and fighting against big business interests.
In contemporary times, politicians such as Bernie Sanders have embodied the progressive challenge to the establishment by pushing for economic equality, universal healthcare, and addressing climate change. These challenges to the establishment often lead to significant changes within political parties, sometimes causing party realignments or influencing major party platforms to reflect more progressive policies.
The rise of progressive movements both in the past and present does, indeed, lead to changes in political parties. They often serve as the catalyst for debates on key issues and influence mainstream policies, although the emergence of a lasting third party remains a complex challenge due to the entrenched two-party system.