When former (and, he hopes, future) Gov. Robert L. Ehrlich Jr. gave one of his semi-annual guest lectures to Towson University Professor Richard Vatz's political rhetoric class on Thursday, he skipped the campaigning and instead served up lessons for the students on how to cut through political spin. It is advice voters would be well advised to take and apply to the candidates in this election — him included.

•Themes. Campaign themes, Mr. Ehrlich said, are shorthand ways for people to identify with candidates without getting bogged down in the specifics. Defining themes is one of the early flash points in this governor's race. Mr. Ehrlich has blasted Gov. Martin O'Malley's contention that his administration has been about making progress, and Mr. O'Malley has targeted the former governor's contention that he will bring Maryland back to better times.

•Symbols. Candidates often try to wrap themselves — or opponents — in symbols to convey messages subconsciously. The former governor used as an example his own campaign stop that morning at a small business in Columbia as a use of symbolism to bolster his theme of job creation. He might well also have mentioned the devastating use of symbols against him by Governor O'Malley in 2006, in particular the frequent use of a picture of the Republican with his arms around then-President George W. Bush.

•Labels. In a trick he uses every semester, Mr. Ehrlich asked the students to raise their hands if they are pro-life. About a third of the class did so. He asked them to raise their hands if they're pro-choice. The other two-thirds did. "You're all wrong," Mr. Ehrlich said, noting that such black-and-white responses fail to capture the complexity of an issue. He said they also make for an easy weapon for opponents to paint you in an unfavorable light. Remember that when Mr. Ehrlich calls Mr. O'Malley an anti-business, tax-and-spend liberal, or when Mr. O'Malley calls Mr. Ehrlich an extreme right-wing protégé of Newt Gingrich.

•Negative ads. Everybody says they hate negative ads, Mr. Ehrlich said, but they still get used in every race. Why? Because they often work. At this point, Professor Vatz chimed in to note that they tend to be less effective when voters have a strong existing impression of a candidate.

So in an election when you've got a former governor running against a current governor, neither side will bother going negative, right? Don't bet on it. But we would all do well to take Mr. Ehrlich's advice to the Towson students and look at them, and everything else in this campaign, with a skeptical, but not cynical, eye.