As any keen observer of this year’s primaries knows, the presidential campaign has already seen its fair share of negative ads. Darrell M. West, a former Brown University political scientist who is now director of governance studies at the nonpartisan Brookings Institution, set out to determine just how negative theprimaries were — as compared with the nine previous White House races since 1972. As it turns out, West found, they weren’t as negative as one might imagine.

West made his determinations by tallying those ads that generated coverage in major print or television media outlets, on the grounds that such commercials are most likely to turn a campaign.

West defined a negative ad as one that attacks a specific opponent by making pejorative or unflattering references to that candidate. Using that definition, he found that both parties’ 2008 campaigns were more negative than is typical, but neither set a record for negativity.

The lengthy Democratic race was outpaced by the 1992 primaries in which Bill Clinton battled former California Gov. Jerry Brown, Sen. Tom Harkin of Iowa and former Sen. Paul Tsongas of Massachusetts, among others. The GOP candidates this year were comparatively kind to one another: Their campaign was only the fifth-most negative in the last four decades — well behind the leader, the particularly nasty duel between George Bush and Patrick J. Buchanan in 1992.