U.S. Sen. Mary Landrieu has been here, or someplace like here, before. She’s faced do-or-die elections and has had to convince a conservative electorate to go with a Democrat. Three times she’s pulled it off, although barely.

Yet this time feels different. Polls and prognostications have varied, but just about all of them suggest Landrieu’s in her toughest fight yet.

It’s not that Landrieu has changed. She’s still routinely ranked as one of the Senate’s few remaining centrists. She still focuses on local issues such as flood insurance and disaster loan forgiveness, and still breaks with Democratic leaders on issues such as fossil fuel.

But the ground sure has shifted. The lines between the parties are more solid. President Barack Obama is notably unpopular among white voters.

You’d expect Landrieu’s GOP opponents, U.S. Rep. Bill Cassidy and tea party candidate Rob Maness, to zero in on Landrieu’s party. What’s more noteworthy is how others are behaving.

Six years ago, Landrieu was able to trot out plenty of local Republicans to vouch for her. This year, fewer are willing to go out on a limb.

Kevin Davis, former president of St. Tammany Parish, endorsed Landrieu in 2008. His successor, Pat Brister, has introduced Landrieu at a fundraiser and offered profuse thanks for forcing the Federal Emergency Management Agency to forgive millions in disaster loans and getting the state a portion of BP penalties, but stopped there.

“I support her,” Brister told the Washington Examiner last spring. “I’m not endorsing her. There’s a big difference. I am not endorsing her, but I support her effort on behalf of citizens that I represent.” Brister declined to elaborate for this column.

Jefferson Parish Sheriff Newell Normand was in Landrieu’s camp in 2008, but this year he, too, is neutral. He said he’s still a fan, still grateful for her support after Hurricane Katrina, still confident that she’ll respond if he calls. But Normand pointed to his own re-election bid next year, then shifted into a discussion of national politics.

Six years ago, he said, the climate was different. “Even for some Republicans, there was hope,” he said, that Obama would lower the temperature.

While Normand likes some Democratic policies — he singled out the Affordable Care Act’s Medicaid expansion, which Landrieu supports, Cassidy opposes and Gov. Bobby Jindal has rejected — he’s got big complaints with how the administration has handled immigration and border enforcement.

“It can’t be that every idea that comes from the other side is a bad idea,” he said. “I thought, ‘You know what? I don’t need to get involved in this thing.’ ”

The state sheriff’s association did give Landrieu its nod, but it was a tougher fight than in the past. Normand, who took part in the negotiations, attributed that to a large contingent of newer sheriffs who didn’t live through the 2005 disaster and who worry that the endorsement could be an issue in their own re-election bids. It was the old guard, he said, who pushed the matter.

Landrieu’s facing similar headwinds at the national level. In prior elections, she’s won the support of the U.S. Chamber of Commerce’s political arm, and a top official there strongly hinted earlier this year that it would back her again even though it is doing its best to take out other vulnerable Democrats. But the news reportedly didn’t go over well in some circles. With just one month to go, the chamber has yet to act, and it’s not clear it will.

Of course, some Republicans are still willing to cross the line on Landrieu’s behalf. Shipbuilder Boysie Bollinger cut an ad contending that “Louisiana can’t afford to lose Mary Landrieu.”

Jefferson Parish Councilman Chris Roberts is back, too. While he disagrees with her on the ACA, Roberts said having Landrieu in Washington has been a net plus.

“I represent coastal communities, needy communities because of natural disasters,” he said. “For me, looking at how unstable national politics is, I think Louisiana has benefited from having representation in both parties. There has never been a time when we called on Mary when she has not responded.”

“I think national politics has everyone on edge,” he added. “I think it has everyone very aggravated. It’s a very unfortunate scenario. I’m trying to look at it not from an emotional standpoint but from a realistic standpoint. What does it do to you to lose that level of seniority?”

If Roberts keeps talking like that, Landrieu may wind up putting him in an ad, too.

It’s not like she’s got a lot of other volunteers from across the aisle.

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