Complex sentence: Some United States Senators (both real-life and fictionals), Democrats and Republicans, were suspected as a part of plot to kill the president, many of them just because they were present in D.C. at certain time.
Split into simpler sentences: Some United States Senators (both real-life and fictionals), Democrats and Republicans, were suspected as a part of plot to kill the President. Many of them just because they were present in D.C. at certain time.