When XIII leans against the wall directly after Kim Rowland is shot you can see flashing blue/red lights through the window but the police do not arrive for several minutes after which you again see XIII leaning against the wall with police lights flashing.
A pay phone is said to be at Dupont Circle, but when shown has the United States Capitol in the close background. In reality, Dupont Circle is approximately 3 miles from the Capitol, more than 20 blocks, so the Capitol would not be visible from a location anywhere around Dupont Circle.
The service mark on the back of key photographs lists the processing shop as being on West 8th Street in Manhattan, but the shop he visits, apparently in Soho, is on or around Houston Street, a good distance south of 8th Street.
The negative campaign advertisement charges that "as Governor of Illinois Joseph Galbrain" voted to cut the Marines, Navy and Intelligence funding. As Governor, he would not have a vote in these matters - only House and Senate members do.
The film sets a General Presidential Election four months after President Sheridan is assassinated on Veterans Day, November 11th, circa March. Federal General Elections have been held on the first Tuesday after the first Monday in November since 1845, set by Act of Congress.