Many of the fired US Attorneys were fired because they weren't sufficiently responsive to GOP accusations of voter fraud against Democrats:
Nearly half the U.S. attorneys slated for removal by the administration last year were targets of Republican complaints that they were lax on voter fraud, including efforts by presidential adviser Karl Rove to encourage more prosecutions of election- law violations, according to new documents and interviews.
Of the 12 U.S. attorneys known to have been dismissed or considered for removal last year, five were identified by Rove or other administration officials as working in districts that were trouble spots for voter fraud -- Kansas City, Mo.; Milwaukee; New Mexico; Nevada; and Washington state. Four of the five prosecutors in those districts were dismissed. [WaPo]
We've known for a long time that voter fraud allegations were a factor in the purge, but the Washington Post is now concluding that the issue was "more central than previously known."
According to the WaPo article, AUSA Steve Biskupic of Wisconsin came within a hair's breadth of termination because Karl Rove deemed him insufficiently responsive to Republican fraud allegations.
As you may recall, Biskupic was responsible for sending Georgia Thompson to prison on trumped up corruption charges. The apolitical Ms. Thompson worked for Wisconsin's Democratic governor. Biskupic alleged that Thompson gave a contract to a particular firm because that firm's CEO gave to the governor's campaign. In fact, the firm submitted the lowest bid. The 56-year-old spent four months in prison and lost her home before a court reversed her conviction.