Final answer:
During the Time of Troubles, there was a major political change in Russia with the replacement of the Romanov dynasty by the Polish nobility.
Step-by-step explanation:
A major political change that occurred during the Time of Troubles in Russia was the change of ruling dynasty. The Romanov dynasty, which had been ruling since the early 17th century, was replaced by the Polish nobility. This change in ruling dynasty had significant implications for the governance and control of Russia.