 In saying (2), Elwood would not say, but merely presuppose, that the sea is salty. In saying (3) he would presuppose, but not say, that someone led America to defeat in the War of 1812. In saying (4) Elwood would presuppose that Bush invaded Iraq, and in (5) he would presuppose that Trump had cheated on his wife, and then stopped doing so for a period of time (possibly rather short).