Typically, an incumbent runs on his record. Occasionally, his opponent will run on that record, too.
That's essentially the theme of the current presidential contest.
President Barack Obama - who had better success than John McCain in convincing voters he was no George W. Bush in 2008 - is running on his accomplishments, and to an extent, so is Mitt Romney, heir apparent to the Republican nomination.
To be certain, criticism occasionally is more personal than professional, as when Obama recently noted he wasn't born with a silver spoon in his mouth.
But far more often, the jabs they take tend to focus on policy. Take, for example, these statements made April 18:
"Their basic mission seems to be one in which a few folks are doing well at the top and everybody else is struggling to get by, but that's okay - that somehow that is a formula for growth," Obama said in Dearborn, Mich.
"We know that it's time to have someone who's actually led, who's spent enough time in the private sector to know how jobs are created and why they leave, and who knows how to bring them back to this country," Romney said in Charlotte, N.C.
This election cycle, if voters find the tone of the contest doesn't match its theme, they should ask whether that tone is set by the candidates, their campaign staffs ... or by observers on the periphery of the campaign who are amplified by biased members of the national media.
Examples for both sides occurred the same week.
Earlier this month, Democratic pundit Hilary Rosen's comments about Ann Romney drew criticism. Days later, Ted Nugent's comments at the NRA national convention drew objections, and attention from the Secret Service.
Then cable news networks seized on one comment or the other and filled airtime for days.
Between now and Nov. 6, we encourage voters to pay attention to claims and statements made by the presidential candidates, and to carefully separate the tone and timber of their campaigns from of advertising by super PACs, left- or right-leaning commentators and the increasingly circus-like atmosphere surrounding the campaigns.