I am wondering whether anyone can assist with a long-standing
etymological puzzle.

In the Presidential election of 1884, the Democrats teased the
Republican candidate, James G. Blaine ("The Plumed Knight"), about the
contemporary version of Watergate involving payoffs, railroad bonds and letters he asked to
be burned. The Democrats jeered "Blaine, Blaine, James G. Blaine/ The Continental
liar from the State of Maine". I have consulted every Blaine
biography written (an amazing 10+), as well as the usual guides and
anthologies.

Not a single one offers any explanation.

My view has always looked to the xenophobia of the period, associating
anything from Europe ("the Continent") as inherently suspect and not
worthy of belief. One of my amateur historian friends looks to our
Revolutionary days, when the debased currency made worthless items
synonymous with a Continental dollar. A professor of American history
at a local college suggested that Blaine's opponents called his lies as
big as the North American continent.

Any clues?