How does the battle over the taft-hartley act demonstrate the constitution's version of checks and balances?

The Taft-Hartley Act of 1947 came after a protracted public battle between all the parties involved in the process of collective bargaining. The political process that led to the Act happened at a time when the Presidency was Democratic and both houses of Congress were Republican. As such, both institutions disagreed on the nature of labor and collective bargaining between different parties. This led President Truman to veto the bill after it had passed both houses of Congress. However, both houses quickly overrode the presidential veto and passed the Act.