He waited two years before making his first move, a suicide run for Congress against an incumbent Democrat.

The teachers' association and the state workers' unions are fielding candidates to challenge incumbent Democrats in this year's elections.

In recent years, political action committees have begun to favor incumbent Democrats over Republicans.

The longtime incumbent Democrat dropped 16 points in the rematch.

But new disclosures of ties to contractors have hurt the incumbent Democrat since.

In Michigan, incumbent Democrats were forced into races against each other.

And to be fair, most incumbent Democrats were returned to their positions of responsibility.

Two incumbent Democrats said they had discovered, embarrassingly at times, what it felt like to be on the minority side of the aisle.

"The incumbent Democrats were not reflecting what so many people in the village feel about this project."

What are the reasons for the extraordinary anger, directed at incumbent Democrats right across the country?