Whenever a major political scandal erupts before an election and voters blame the scandal on all parties about equally, virtually all incumbents, from whatever party, seeking reelection are returned to office. However, when voters blame such a scandal on only one party, incumbents from that party are likely to be defeated by challengers from other parties. The proportion of incumbents who seek reelection is high and remarkably constant from election to election. If the voters' reactions are guided by a principle, which one of the following principles would best account for the contrast in reactions described above? ['Major political scandals can practically always be blamed on incumbents, but whether those incumbents should be voted out of office depends on who their challengers are.', 'When a major political scandal is blamed on incumbents from all parties, that judgment is more accurate than any judgment that incumbents from only one party are to blame.', 'When major political scandals are less the responsibility of individual incumbents than of the parties to which they belong, whatever party was responsible must be penalized when possible.', 'Incumbents who are rightly blamed for a major political scandal should not seek reelection, but if they do, they should not be returned to office.']