On Nov. 4, millions of voters across America will pick the winners in campaigns for the U.S. Senate, U.S. House, governor and more.

And in the two competitive U.S. House races in Louisiana, hard-charging Republican candidates will leave no stone unturned in their drives to ... finish second.

Thanks to the vagaries of Louisiana elections law and the dynamics of the contests in the 5th and 6th congressional districts, the runners-up there on Nov. 4 could emerge as strong favorites for the final balloting on Dec. 6. And in both cases, odds are good that the runner-up will be the top vote-getter among several Republicans in the field.

“These two races have a lot in common,” said Pearson Cross, head of the political science department at the University of Louisiana at Lafayette. “Whoever manages to get into the general election against the Democratic candidate is the putative favorite.”

In Louisiana, that general election is Dec. 6, matching the top two vote-getters from the Nov. 4 contest, which includes all candidates regardless of party (a candidate winning a majority Nov. 4 avoids a runoff, but that’s considered unlikely in the two House races).

Both districts are Republican-leaning and conservative. But in both districts, one major candidate has emerged on the Democratic side while several are squabbling over the Republican vote. That suggests the Democrat will finish first Nov. 4 with the solid backing of the district’s Democratic minority, while the Republican candidates will split the votes of the majority Republicans so that even the front-runner among them will lag the Democrat — yet that top Republican will be in the driver’s seat in a one-to-one showdown with the Democrat.

The election in the 6th District, which extends from Baton Rouge north to the Florida Parishes and south to Houma, features the dominant Louisiana politician of the half-century — the previous half-century. That would be Democrat Edwin Edwards, the four-time governor and eight-year federal prison inmate, who is bidding for a political comeback at age 87.

“The great irony here is that Edwards has no chance of winning the seat, but he is likely to finish first in the November balloting,” said David Wasserman, the expert on House races for The Cook Political Report in Washington.

Edwards seems destined to lose Dec. 6 to whomever finishes second to him — but first among the Republicans — on Nov. 4. The leading contenders are Garret Graves, a former aide to Gov. Bobby Jindal who has collected an impressive amount of campaign cash, and state Sen. Dan Claitor, of Baton Rouge. Incumbent Bill Cassidy, a Republican, is running for the U.S. Senate.

By contrast, the 5th District race includes the incumbent, who is a Republican: Vance McAllister. Normally, that would assure an easy victory. But McAllister, who won a special election last year to fill a vacated seat, was captured this spring on closed-circuit TV smooching with a staff member from his district office. Both he and she were married, though not to each other.

“Obviously, he will be criticized for being caught in a scandal,” said Joshua Stockley, who teaches political science at the University of Louisiana at Monroe, in the 5th District, which covers the northeast quadrant of the state. “He ran on a Christian, family values platform. Being caught on video kissing a staff member obviously opens yourself up to how ‘Christian’ and ‘family values’ are you.”

McAllister got a boost in 2013 from an endorsement by the Robertson clan of “Duck Dynasty” TV fame. But this year, the Robertsons are putting their money behind a relative: Zach Dasher, a pharmaceutical sales representative who is one of several Republicans making the race.

The Democrat candidate is Monroe Mayor Jamie Mayo, who was squeezed out of the runoff in 2013 by McAllister. Unlike last year, no other Democrats have jumped in, and Mayo could very well finish first on Nov. 4.

McAllister is still the candidate to beat among the Republicans, thanks to his name recognition and the vote-splitting effect of his multiple Republican challengers. And Wasserman and Cross think McAllister would dispatch Mayo pretty easily.

Stockley, though, can see a path to election for Mayo, paved by divisive competition among the Republicans and success in unifying Democratic voters and moderates.

“That’s a tall task,” Stockley acknowledged, “and I’m not saying he has a great chance.”

Gregory Roberts is chief of The Advocate Washington bureau. His email is groberts@theadvocate.com. Follow him on Twitter, @GregRobertsDC.