The Constitution's Speech or Debate Clause is important because it offers protection to the members of the United States' Legislative Branch to speak and discuss affairs germane to the state's functioning without fear of punishment. As the clause ensures that the members of the Legislative Branch engage in "...any Speech or Debate in either House, [senators and representatives] shall not be questioned in any other place," it guarantees a sense of freedom in thought and action. The framers understood the need for members of the legislative branch to be able to form policy and discourse without fear of apprehension or silencing of voice. Given how the Legislative Branch is the seat of all policy for the nation, the Speech or Debate clause is essential because it enables freedom of thought to transpire without repressive tendencies. It is also significant because it shows the Legislative Branch as something that cannot be dissolved or silenced in times of challenge. The framers understood that the political tendency of centralized authority is one that might move towards seeking to silence or eliminate the legislative branch. With its emphasis and protection of freedom, the speech and debate clause prevents this from happening, demonstrating its importance.
This clause was much more important in times past than it is today. Today, our habits of democracy are rather well instilled in us and there is little real danger of this clause being violated in important ways. However, the clause was very important at the beginning of our country’s history because it emphasized the importance of legislative independence.
The main point of this clause was to prevent presidents from exercising too much power over the Congress. It was meant to, for example, prevent the president from having members of Congress arrested so that they could not get to the Capitol and cast a vote that the president did not like. The Framers of the Constitution were still worried about presidents using their power to achieve the status of dictators. For this reason, they included the Speech or Debate Clause.
So, the importance of this clause was that it helped to prevent Congress from losing its independence to an overbearing president. It is no longer very conceivable that a president would act in this way, so this clause is not as important today as it once was.