Nothing Sarah Palin says tonight ought to have much bearing on the question of whether she's qualified to be vice president. But as a political matter she does have the ability at least change the mocking media dynamic around her selection, which is currently being shaped by bloggers and TV pundits.
Above all, Palin must seem confident. Life is in many ways a confidence game. It's like the old rule of getting past an intimidating doorman--acting like you belong inside is half the battle. One reason Republicans were so impressed with Palin initially is that she gave a feisty, chin-up, and cleanly-executed speech when McCain introduced her last Friday. Tonight's speech will be a test of how the woman handles extreme pressure. If she comes across as nervous or ill-prepared, it's lights out. (How can Republicans expect her to stand up to Joe Biden in a debate if she fumbles her teleprompter lines on the big stage?)
Beyond that, there are three main areas to watch for, and two narrower points:
Experience: Palin needs to tell stories demonstrating that she has done heavy lifting in government, and been tested under fire before. This will require some artful dramatization of her career in Alaska politics. The trick will be making her political fights seem more significant than they were without resorting to ridiculous hyperbole.
Foreign policy: Can a controversial US Weekly cover girl speak credibly about America's role in the world? Again, this is a speechwriting challenge. Palin has to sound fluent and confident in foreign policy issues without the comedic overpreparation of, say, Paris Hilton talking energy policy poolside in a bikini. There may be a temptation to name-check Waziristan and a list of obscure foreign leaders, but for now she's probably best-off sticking to broad conservative themes of American leadership and strength. Wait for the inevitable pop-quizzes that will come when she sits for TV interviews.
Biography + Economy: One good criticism of the GOP convention to date is how little attention its given to kitchen-table issues. Palin's speech is an opportunity to change that in a high-profile way. Look for her to tell a good American story about a woman of humble origins with high aspirations working hard, playing by the rules, and making something of herself. The people with whom this story likely resonates most are also the people feeling the hardest pinch these days. Next Palin can shift to her life today, as the working mother of a big family with (apparently) little room to spare in its budget. If I'm her speechwriter I'm looking for any and every bit of economic sacrifice she's made in the past several years. References to Hamburger Helper strongly encouraged, for instance. (And this of course has the added effect of diminishing the McCain estates storyline.)
Go Easy on Obama: Running mates are typically employed as attack dogs--recall how Joe Biden lit into McCain on the very day he was chosen. But McCain can't afford to seem nasty right now. She needs to clean up her own image first. At most, she's got room for a jab or two--but she should make it humorous.
Girl Power: Work in feminist-y historic-trailblazer language like she did in Dayton last week. It excites conservatives who have felt stuck on the losing side of Obama's historicality, jazzes up the media, and confounds her liberal critics
One speech can't dispel the fundamental doubts about Palin's qualifications. But a command performance may give the media pause in going after her as a lightweight, and will encourage Republican surrogates to climb father out on a limb in their public support of her. At this point, until it finds out whether any more shoes will drop from her quirky past, that's the best the McCain campaign can hope for.