It has never happened before.
It almost certainly will never happen again.
Calling it a fluke is hardly unreasonable. Calling it a rare confluence of circumstances in 2008 would, however, be reasonable, and certainly accurate.
“It” was the unprecedented general election triumph in Nebraska’s Second Congressional District (Douglas County and roughly the northeast half of neighboring Sarpy County) by Barack Obama, the Democratic presidential nominee. An unofficial final count had Obama winning the district by 3,325 votes.