How can the Nature of Power change between the Presidency and Congress?

-At the Beginning, the 'Imperial Presidency' may be Noted where the President is more Powerful than Congress. This can happen after a Presidential Election or a National Crisis -Power may be Split Evenly with the 2 Branches, leading to Bipartisanship or Gridlock. This may be seen during Midterms or as the President gets less Popular. -Potential 'Lame Duck' Presidency where Congress becomes too Powerful to handle. This can be common during the End of the Presidency, or when Control of Congress is the Rival Party