Democrats have insisted that they will push to win the only outstanding Senate race in the country — a Dec. 10 runoff election in Louisiana — but it appears to be trending toward the Republican candidate, which would give the party an effective 52-48 majority next year.
State Treasurer John N. Kennedy won the most votes on Nov. 8, but in a crowded field he fell far short of the 50 percent threshold needed to win outright.
Foster Campbell, a Democrat and member of the Louisiana Public Service Commission, placed second, setting up a showdown that Democrats hoped could pare the Senate Republican majority to just a single seat.
The latest polling, though, shows Mr. Kennedy with a massive advantage, and he appears eager to nurse his lead and ride the aftershocks of the surprise wave that powered Republican Donald Trump to the presidency.
Mr. Campbell says Mr. Kennedy is ducking the voters and that his campaign is banking on his independent streak to pull off an upset in a state that Mr. Trump carried by nearly 400,000 votes over Democrat Hillary Clinton.
“Foster Campbell doesn’t toe a party line. He is his own man, and he has the record of clear results to prove it,” campaign spokeswoman Mary-Patricia Wray said.
Even so, political analysts say Republicans are poised to keep the seat being vacated by retiring Sen. David Vitter.
Republicans also are also on track to retain two House seats in next month’s runoffs. Republican Reps. John Fleming and Charles W. Boustany Jr. vacated their seats to run for Mr. Vitter’s Senate seat.
Republican contender Clay Higgins is leading fellow Republican Scott Angelle, by 7 percentage points in the race for the 3rd District seat held by Mr. Boustany, according to a poll by the Trafalgar Group. The same survey also showed Republican Mike Johnson is thumping his Democratic opponent, Marshall Jones, by 25 points in Mr. Fleming’s 4th District.
The Trafalgar poll also said Mr. Kennedy, who has built name recognition during his 16-year tenure as state treasurer, leads Mr. Campbell by 23 percentage points, 58 percent to 35 percent.
“National Democrats do not seem very interested in diverting funds to Louisiana. Campaign operations sometimes make mistakes, but that’s probably a telling sign that they do not see a path to victory for Campbell,” said Kyle Kondik, managing editor of Sabato’s Crystal Ball at the University of Virginia. “There’s not much, if any, indication that Democrats have much of a chance to pull an upset in the Louisiana runoffs.”
The runoffs are byproducts of the unique system in the Bayou State that dispenses with party primaries in favor of one race in November, and then requires the top two finishers, regardless of party affiliation, to hold a runoff should nobody win a majority on Election Day.
The Senate race offers Democrats a final chance to make up ground against Republicans. Democrats netted just two seats, short of the five needed to regain control of the chamber.
“We’re not taking anything for granted. We’re going to run as hard in the runoff as we did in the primary,” said Kennedy campaign spokesman Lionel Rainey III.
Democrats look to last year’s governor’s race for hope. In that battle, John Bel Edwards defeated Mr. Vitter, whose gubernatorial bid faltered amid accusations about his character after a prostitution scandal in 2007.
The state is reliably red in federal elections but has only one Democrat in its congressional delegation. In 2014, Bill Cassidy swiped Louisiana’s other Senate seat from three-term Democratic incumbent Mary L. Landrieu.
The Campbell campaign said he outperformed Ms. Landrieu that day by attracting more than 60 percent of the vote in his re-election bid to the Public Service Commission, which regulates utilities, in the 24 parishes he represents, compared with Ms. Landrieu’s 42 percent in those districts.
The campaign says its internal polling shows it is running closer than Trafalgar’s numbers suggest and is betting the race will tighten down the stretch.
Republicans don’t want their edge to erode any further because every seat they have is an insurance policy against Democrats’ attempts to peel off GOP defectors when contentious issues come to the floor.
“The difference between a two- or four-vote cushion in the U.S. Senate is huge, especially when it comes to advancing the conservative agenda,” Mr. Rainey said. “Having John Kennedy in the U.S. Senate will be vital to securing our border, defeating ISIS, repealing and replacing Obamacare and reducing the tax burden on the middle class and job creators.”