Well last time it happened (2012) the conservative party won the congress in April 2012 and then went on to win the presidential election in December ... the elected person was Park Geun-Hye, widely considered the worst leader in decades, and was impeached among corruption scandal four years later.

Maybe that's an argument for staggering elections even more regularly, or maybe it's just one of those coincidences pundits love to talk about, I don't know. :)