There’s a saying that “All politics is local.”

That may yet prove to be the case in this year’s election for the U.S. Senate in Louisiana, but it’s hard not to see the race playing out against a national landscape.

The big prize nationally in this nonpresidential election year is control of the U.S. Senate. It’s a given that the Republicans will keep their majority in the House, and they dearly wish to bring the Senate into their fold. They need to pick up six seats to do it, and central to their strategy is knocking off Democratic incumbents in states that voted for Republican Mitt Romney in the 2012 presidential election.

That puts U.S. Sen. Mary Landrieu squarely in their crosshairs. A three-term incumbent, she is the last remaining Democrat elected statewide in Louisiana, which favored Romney by 58 to 41 percent over Democratic President Barack Obama.

So plenty of money from national conservative political groups is flowing into the state to pay for anti-Landrieu commercials, and the candidate of the Republican establishment, U.S. Rep. Bill Cassidy, of Baton Rouge, is running a well-financed campaign. Landrieu herself is backed by outside money from liberal and Democratic sources. Her campaign has raised more than Cassidy’s in direct contributions, according to the most recent finance reports, but it has spent more, too, and each has about the same amount of cash on hand, with polls showing the two candidates in a close contest.

Then there’s the Obama effect: He’s an unpopular president, and Democratic candidates suffer from guilt by association, especially in red states. Plus, there’s the historical pattern of an incumbent president’s party faring poorly in congressional elections midway through his second term.

Viewed from those perspectives, Landrieu faces an uphill climb. But she’s overcome the odds before: In 2008, when Obama lost by an even wider margin at the top of the Democratic ticket in Louisiana, she won with 52 percent of the vote, which, compared to her previous Senate races, was a landslide.

Landrieu, 58, must be hoping that saying about politics being local holds true. She has campaigned vigorously across the state, and her Senate office has poured forth a steady stream of announcements of federal money going to parishes, cities and businesses, from $225 million for Coast Guard cutters in Lockport to $24,000 for firefighters in Ruston.

Although the banning of budgetary earmarks a few years ago makes it more difficult for her to claim direct credit for the largesse, she is a classic, old-school, bring-home-the-bacon senator, which has won her the support of many ordinarily Republican businessmen — most notably Boysie Bollinger, the Louisiana Republican Party stalwart whose shipyard happens to build those Coast Guard cutters. The daughter of a former mayor of New Orleans and the sister of the current one, Landrieu has held state and federal office in Louisiana almost continuously for 35 years, and hers is a household name.

By comparison, Cassidy, 56, has run a low-key campaign. A physician, third-term congressman and former state senator, he’s behaved more like an incumbent than Landrieu — so far agreeing to just two candidate debates, while she has signed up for five — and seems to be banking on the rising Republican tide to carry him forward as he avoids rocking the boat.

Pearson Cross, chairman of the political science department at the University of Louisiana at Lafayette, says Cassidy should be careful about playing his cards too close to his vest.

“He needs an aggressive campaign to upset a three-term United States senator — even one that hasn’t been elected by wide margins,” Cross said. “To beat somebody, you’ve got to come with something.”

But sharp divisions over policy have not driven the campaign to date.

Landrieu and Cassidy certainly disagree on some issues: She voted for the Affordable Care Act, commonly known as “Obamacare,” while he has voted repeatedly to repeal it, and he sponsored a bill passed by the House just this past week that would delay the law’s mandates for employee group insurance plans for five years (the sort of “you can keep your plan” legislation that Landrieu has said she favors). But Obamacare is subsumed under anti-Obama sentiment generally and, in any case, is fading as a major issue for Republicans nationally.

Landrieu and Cassidy also differ over reproductive rights, but opinions there may well be so settled among the electorate that the issue won’t sway the voters on the fence that both candidates are courting.

Republicans have sought to score points off Landrieu over her illegal use of taxpayer money to pay for campaign air travel, which she has blamed on bookkeeping errors and acted to correct, and her ownership of an expensive house in Washington as her principal residence. Those attacks certainly have not helped Landrieu, but for a candidate as well-known and identified with Louisiana as she, their effect may be minimal.

On a number of issues, Landrieu and Cassidy agree: They both support completion of the Keystone pipeline. They’re both leery of environmental regulations on the energy industry. And they worked together to mitigate the impacts of flood insurance reform.

That has left them to wrangle over how effective Landrieu is in the Senate: She touts her ascension this year, by virtue of her seniority, to the chair of the Energy and Natural Resources Committee, with its oversight of the oil and gas industry that is central to the Louisiana economy; he says any of her potential clout is neutralized by the anti-energy Democratic majority in the Senate that Landrieu helps provide.

Landrieu is one of the more conservative Democratic senators, especially on energy policy, which helps explain the lack of sharp contrast with Cassidy, a relatively moderate Republican.

“She could switch her party tomorrow, as a Republican, and win,” said Joshua Stockley, a political science professor at the University of Louisiana at Monroe. “Her stance on the issues would be almost completely consistent with her (new) party. She acts like a Republican already.”

But Landrieu’s problem is that she is not a Republican, Stockley said.

“She has a letter behind her name, D, and it’s toxic,” he said. “It is incredibly toxic being a Democrat in the South.”

Complicating the U.S. Senate election is Louisiana’s open primary system and the state’s election schedule. Landrieu, Cassidy and six other candidates will run in the same field Nov. 4, the final election day in most of the rest of the country. If no candidate wins a majority of the Nov. 4 vote, the top two finishers meet in a runoff Dec. 6.

Making a runoff more likely is the presence on the ballot of Rob Maness, a tea party Republican who has not held elective office before. Although Maness — who says he’s accepted invitations to more than a dozen debates and forums — lags well behind Landrieu and Cassidy both in fundraising and in the polls, he is drawing enough support to reduce the odds of the Nov. 4 vote producing an outright winner. Landrieu and Cassidy are close in most voter surveys, but neither has looked likely to broach the magic 50 percent mark on Nov. 4.

Maness, who calls himself the true conservative in the race, is a thorn in the side of Cassidy, whom Maness attacks as a part-of-the-problem member of the Washington establishment. Because of Maness, Cassidy’s chances to win without a runoff are slim. And the more Maness stirs up tea party wrath toward Cassidy, the less likely that Maness’ supporters will turn out for Cassidy on Dec. 6.

The Cassidy campaign won’t acknowledge its strategy, but it’s near-certain Cassidy’s vision of a path to victory ends on Dec. 6. The path is steeper if Republicans fall short of a five-seat gain in the Senate in the rest of the country Nov. 4: In that case, voters in a runoff would choose between returning an incumbent as chair of the Energy and Natural Resources Committee or electing the most junior member of the Republican minority to represent them. If Republicans seize the Senate on Nov. 4, the picture flips, with Landrieu losing her committee chair and a major argument for her re-election.

If control of the Senate rides on the Dec. 6 vote, an enormous amount of attention — and money — will be focused on the state for that event. Charlie Cook, of the Cook Political Report in Washington, thinks that scenario favors Cassidy, as the Republican candidate in a red state in a generic partisan matchup for Senate supremacy. Stockley isn’t so sure, predicting national Democrats will bring in their heavy artillery to match the Republican battalions. (There’s yet another wild card in here: The Senate race in Georgia, which polls show is close, could go to a runoff Jan. 6.)

The Landrieu campaign won’t acknowledge its strategy, either, but it’s just about as certain Landrieu is targeting Nov. 4, and an outright win that day.

“It would be a surprise for anybody to win this without a runoff,” Cook said, “but for Landrieu, I think they need to swing for the fences.”

And Landrieu’s fate on Nov. 4 rests on a factor that’s key in any election but poses a particularly thorny problem for her in this one: voter turnout.

Midterm elections like this one draw considerably fewer voters than presidential elections. In the 2012 presidential election, 2 million voters in Louisiana cast ballots. In the 2010 midterm election, topped by the race for Louisiana’s other U.S. Senate seat, just 1.5 million voters participated.

Beyond the totals, the makeup of the electorate changes. For example, black voters, who make up 31 percent of the Louisiana electorate and are a traditional source of support for Democrats, turned out at nearly the same rate as white voters in 2012: 67 percent, compared to 69 percent for white voters. In 2010, white voter turnout was 48 percent — but black voter turnout was significantly lower, at 39 percent.

“In a midterm election,” Cook said, “the turnout is older, it’s whiter, it’s more conservative, it’s more Republican.”

Landrieu’s challenge, then, is to buck that trend.

Democrats have developed sophisticated and effective mechanisms to get younger and minority voters to participate in elections — their success is one reason Republicans were surprised by Romney’s defeat in 2012 — but those efforts have been concentrated on swing states in presidential elections. Landrieu’s chances for a fourth term in the Senate likely rest on her ability to apply those techniques in Louisiana on Nov. 4.

Follow Gregory Roberts on Twitter @GregRobertsDC. For more coverage of government and politics, follow The Advocate Politics Blog at http://blogs.theadvocate.com/ politicsblog/

Editor’s note: This story was changed Sept. 14, 2014, to reflect that there are eight candidates in the U.S. Senate race after the Rev. Raymond Brown, a Democrat from New Orleans, announced last week that he withdrew his candidacy, although the Secretary of State’s Office has not yet acknowledged the change.