Woodrow Wilson was President of the U.S. after Mark Twain had already
died...."resigned" means to have left, or quit a "position", which in this
case means a job, or a duty, and in this case, they are being facetious, and
elected simply means to have been chosen, either directly through a vote of
the people, or as in this dialogue, indirectly by someone else having left
the position to those upon whom it must fall...those left behind.
    -David DePauw