In her New York Times article "When Congress Was Armed and Dangerous," Prof. Joanne Freeman of Yale University notes that the violent American political culture of the current (Tea Party) era has a clear antebellum precedent. In the mid-nineteenth century, Freeman writes, it was increasingly common for Congressmen to carry weapons with them in public and in the halls of Congress, and in at least two cases in the 1850s a legislator either drew a gun on a colleague or thrashed a Senator to unconsciousness.
On closer examination, however, the political violence of the 1830s, '40s and '50s appears to have been mostly rhetorical, a display of violent masculinity that probably impressed the voters but didn't actually threaten more than a few Senators and Congressmen. Indeed, it's rather surprising how few of the 10,000-plus men and women who served in the American Congress since 1789 actually died of non-natural causes while in office. Congress.org reports that 50 or so serving Congressmen and Senators died in vehicle crashes or killed themselves, and only ten were victims of homicide. Of those ten, three died in duels, one (Senator Baker of Oregon) died in the Civil War at Ball's Bluff, one was shot "by an insane son," one was shot by religious cultists and Kool-Aid connoisseurs, and four (two Senators, Long and Kennedy, and two Congressmen) were assassinated. In noting this, I don't mean to imply that Americans are peaceful, just that we prefer to direct violence against people who are weak (like the reporters mentioned in Freeman's essay) or belong to racial minorities (Chinese immigrants, African-American freemen and slaves, Native Americans). Generally, Congressmen and Senators haven't met either of these specifications. While saying so will bring no comfort to Rep. Gabrielle Giffords and her family, it's a pretty safe job.