OPINION — This is the golden age of political horoscopes — sophisticated projection systems designed to forecast the 2018 elections.

Whether primarily based on the generic ballot (voters currently prefer the Democrats by an 8-point margin) or detailed rundowns of individual races (roughly three dozen GOP-held seats are seriously imperiled), these forecasts all assume that no major external events will upend the political mood before Election Day.

But even before Russian meddling, the outside world — including the economy and unexpected scandals — was rarely respectful of the sanctity of the American electoral system.

For example, during the week before the 1956 elections, Israel (aided by Britain and France) invaded Egypt and seized the Suez Canal. And Soviet tanks rolled into Hungary to crush the popular uprising calling for the creation of a multi-party democracy.

These two grave international crises — still unfolding as the voters went to polls — contributed to Dwight Eisenhower’s landslide re-election victory and a status-quo verdict in the congressional balloting.