President Obama's fiercest conservative critics call his administration "one of the most corrupt" in the nation's history, says political scientist Brendan Nyhan at Sabato's Crystal Ball. But what distinguishes the Obama White House is its lack of scandals —  something that has marred every American presidency since Watergate. Since 1977, the longest any president has gone without a major scandal featured on the front page of The Washington Post has been 34 months — the period between George W. Bush's first day in office in 2001 and the eruption of the Valerie Plame scandal in late 2003 (a nearly three-year honeymoon no doubt extended by the shock of Sept. 11). Obama has already gone nearly that long, which means it's a virtual statistical certainty he'll be stained by scandal, too. But how has he stayed clean? Here, an excerpt:

Obama's vulnerability has been mitigated by the number and magnitude of competing news stories. Just as slow news periods seem to encourage scandal coverage, my research shows that pressure from competing stories diverts attention and media resources that could have been devoted to negative coverage of the administration.... In Obama's case, it is clear that external events have consumed much of the news agenda over the last eighteen months, including the Deepwater Horizon oil spill, the Arab Spring revolts, the shooting of Rep. Gabrielle Giffords, the earthquake and tsunami in Japan and the killing of Osama bin Laden. The saturation coverage that these stories received left little room for scandal, particularly given the volume of debate over the merits of the president’s legislative agenda and his confrontation with the new Republican majority in the House.

Read the entire article at Sabato's Crystal Ball.