Two weeks before her name appeared on a ballot in Washington state's Democratic primary, Deborah Senn, a candidate for state attorney-general, became the target of a $1.5m television advertising campaign that accused her of engaging in a "cover-up" with state officials over a $700,000 insurance fine she had suspended during her tenure as a state insurance commissioner.

Ms Senn, who had a reputation for being tough on business, survived the attack and won the primary, but ultimately lost her bid to a Republican opponent.