I wouldn’t dare guess the outcome of Louisiana’s high-stakes U.S. Senate race, other than to say I’m quite sure it will be a nail-biter.

But there is one thing I can predict with some confidence: If Democrat Mary Landrieu loses the seat she’s held for 18 years, it won’t be because of “chartergate.”

That won’t be for lack of effort on the part of Republicans.

Seizing on news reports that Landrieu’s Senate office improperly paid for several campaign-related charter flights using taxpayer funds, GOP operatives are trying their best to turn an obviously bad situation into a full-blown scandal. The national Republican Party’s in-state operative sent mocking emails to reporters, with headlines like “Air Mary scoffs at $20k bill.” Landrieu’s leading challenger, U.S. Rep. Bill Cassidy, cited it in his fundraising appeals. Activists in pilot and flight attendant costumes showed up to greet her when she qualified for re-election last week.

But here’s their problem: There’s no evidence that Landrieu knew about the bills or that she hatched some nefarious scheme to shift costs from her very healthy campaign account to the public purse. The situation appears to be what she says it is, an embarrassing staff error, one that she’s now vowed to investigate and fix.

And here’s their bigger problem: Landrieu isn’t exactly a blank slate.

If Landrieu were still making a first impression, this is the sort of thing that could do some damage. Think Texas Gov. Rick Perry flubbing simple debate questions before a national audience, or Gov. Bobby Jindal blowing his televised response to President Barack Obama’s first address to Congress.

But while Landrieu’s approval rating has been known to rise and fall with the political winds, it’s not because voters don’t know what she’s about.

In fact, her career has been marked by remarkable consistency. She’s a classic red-state Democrat, one who sometimes votes with her party and sometimes breaks with it, who focuses a lot of her attention on local priorities, such as disaster recovery and energy, and who tries to steer clear of ideological showdowns. And who, by the way, doesn’t have a history of the sort of self-dealing her opponents are hyping.

She’s also, at this point, very much a Washington insider. Her critics say this incident demonstrates that she’s lost touch, and they’ll surely find an audience for that point of view. Chances are, though, it’s made up of people who already don’t like Landrieu, who don’t see much value in her long tenure.

Landrieu’s entire campaign is aimed at appealing to those who do, who view her seniority as not just a plus but as something worth crossing party lines to safeguard.

She’s got the Democrats, those who are happy when she votes for things like the Affordable Care Act and who understand that she can’t be with them on all their issues and survive in this state. What she needs are the crossover voters, the people who want a senator with the longevity to have ascended to the chairmanship of the Energy Committee, who appreciate her centrism and record of bringing home the bacon, who recognize the importance of “clout” — which, by the way, seems to be her new, focus-group-tested catch phrase.

Cassidy’s counter-pitch is that Landrieu’s out of step with the state’s politics, that her clout doesn’t translate to influence on issues where she disagrees with her own party and that she doesn’t break with the president and the Democratic leadership often enough. He’s running as a Republican above all, one who’d help block Obama’s policies at every turn and help the GOP take control of the chamber. His efforts have been complicated by attacks from fellow Republican Rob Maness, a tea party favorite who insists Cassidy’s not sufficiently conservative, but this remains a pretty straightforward showdown between two competing ideas of what a Louisiana senator should be.

And it’s going to take something much more dramatic than a bookkeeping error — even a really embarrassing one — to alter the storyline.

Stephanie Grace can be contacted at sgrace@theadvocate.com. Read her blog at http://blogs.theadvocate.com/gracenotes. Follow her on Twitter, @stephgracenola.