Any U.S. voter who missed the Democratic and Republican national conventions can be excused. Those quadrennial affairs are tightly choreographed infomercials that rarely reveal true insights into the candidates. Both parties have refined the art of tamper-proof campaign packaging: Clint Eastwood moments are few and far between and will only get fewer and farther between in the wake of that unvetted departure from script.

Likewise, voters who have yet to see a television commercial for one of the presidential candidates haven't missed a thing. Those 30-second messages are long on imagery and short on useful specifics.

But presidential debates -- those are different. As exhaustively rehearsed as the candidates may be, there's always room for some new, telling bit of information. A policy detail not previously delineated, a charge not previously unleashed. Debates may have their limits but they also offer voters a window into the candidates' character, mental acuity and fight.

And now the 2012 presidential debates are upon us. Barack Obama and Mitt Romney will go at it for 90 minutes tonight starting at 6 p.m. Pacific time from the University of Denver. Jim Lehrer, host of "PBS NewsHour," will moderate the debate, which will focus on domestic policy. The vice presidential debate follows eight days later in Danville, Ky.; and Romney and Obama face off again Oct. 16 at New York's Hofstra University and Oct. 22 in Boca Raton, Fla.

Most pundits agree that Romney needs a game-changer. He's trailing in most polls by 3 to 7 percentage points in virtually every swing state, so it'll probably take a decisive victory tonight over the surging incumbent to turn things around. But Romney can play on two strengths: one, Obama hasn't participated in a real debate for four years, but Romney fared well in a series of debates against Republican opponents just a few months ago; and Romney will have an easier target against Obama's record as president than Obama will have taking aim at Romney's record as Massachusetts governor in 2003-07. We're sure he'll try anyway.

The bottom line is this: Presidential races take place in the protective bubble of campaign consulting teams, poll evaluation and advertising strategy. The debates are less so: They are as close as we'll get to candid evaluations of the unvarnished candidates. They are not to be missed by engaged voters.