U.S. senatorial candidate Rob Maness might be both a fine fellow and a solid conservative, but there are good reasons why some Louisiana conservatives wish he would exit his race. Most of those reasons involve conservatives’ desire to see incumbent Mary Landrieu finally evicted from office. The peculiar nature of Louisiana’s open primary makes it more likely Landrieu eventually will be re-elected if Maness keeps running.

First, let’s be clear: Maness is not running the sort of campaign that recommends him for high office. His résumé of honorable military service as a full colonel, combined with several advanced degrees and a couple of years in business, is admirable, but his campaign has been less so. Instead, it repeatedly has resorted to juvenile stunts and mischaracterizations of other candidates’ statements and positions.

The usual target of these mischaracterizations has been Landrieu’s leading challenger, Rep. Bill Cassidy. In January, the Maness campaign accused Cassidy of telling the Republican State Central Committee that he would serve political insiders rather than the general public if he got elected and also of saying that he thought he would lose to Mary Landrieu in a December runoff. As reported by The Hayride blogsite, both contentions were demonstrably false.

There’s more: Maness wrongly accused Cassidy of being “silent” on the issue of the Benghazi terror attacks. Maness’ campaign contended at bizarre length that Cassidy had falsely claimed a public event was Cassidy’s own “meet and greet.” (1. Cassidy had not done so. 2. Who even cares?) And Maness criticized Cassidy not from the right but from the “politically correct” left for daring to say that liberal U.S. Senate Majority Leader Harry Reid runs the Senate like a “plantation.” Oh, the horror, the horror! Maness’ attack was so ham-handed that a Louisiana Tea Party group, supposedly Maness’ base constituency, blasted Maness (by clear implication) for his breathless denunciation of Cassidy’s rather innocuous statement.

We’ve all seen high school student government campaigns more high-minded than this.

So if a campaign full of what the Hayride’s Scott McKay calls “rookie mistakes” helps explain why Maness hasn’t caught fire, the next question is, how does his presence help Landrieu?

By most people’s reckoning, any votes Maness gets in November will come straight from Cassidy’s hide and will almost assuredly push the election to a December runoff. Outside analysts say that should help Cassidy because strangely timed runoff elections supposedly suffer from low turnout, which supposedly benefits Republicans. But those analysts are wrong.

First, when the runoff is the only race in the country, it attracts so much national attention that turnout doesn’t drop. Consider Landrieu’s successful re-election bid in 2002: Turnout in the primary (1,246,333) and runoff (1,235,296) were nearly identical.

Second, especially this year, Landrieu more than Cassidy will benefit from national attention and money. In November, she will be only one of about a dozen seriously endangered Democratic Senate incumbents. The national Democratic attention will be split 12 ways. As Democrats tend, more than Republicans, to depend far more on paid Election Day street workers (which is legal), the 12-way division of focus leaves her far less protected than she would be in a December runoff. In December, as the only race in the country, the entire organizational might of national Democrats and their union allies can be bused in to turn out her vote.

Meanwhile, what seems to be a developing anti-Obama wave, dragging Democrats like Landrieu down with it, may well crest in November. If Republicans gain a Senate majority then, much of their energy could dissipate by December, while the Democrats’ enthusiasm for salvaging one final bright spot could be quite high.

Indeed, in the recent history of December runoffs, the party that has “lost” the November elections has usually won the after-thought runoffs. That’s what happened, for example, in Georgia Senate races in 1992 and 2008, and in Louisiana in 2002 (Landrieu herself, in an otherwise mildly Republican year) and in the New Orleans-area congressional race (Republican Joseph Cao) in 2008.

Maness might have a decent future in state politics if he plays his cards right. But if he keeps running a campaign that eventually gets blamed for saving Landrieu’s skin, Republicans will never forgive him.

New Orleans native Quin Hillyer is a contributing editor for National Review. You can follow him on Twitter, @QuinHillyer. His email address is qhillyer@theadvocate.com, and he blogs at blogs.theadvocate.com/quin-essential.