Replicating that winning formula could depend on what matters more to voters: Landrieu's growing ability to help Louisiana's oil and gas industry through her recent promotion to chairwoman of the Senate Energy and National Resources Committee or her unapologetic vote for President Barack Obama's health care overhaul.
The answer means much to the balance of power in Washington in the final two years of Obama's presidency. Republicans need to gain only six seats to grab control of the Senate and, with the House likely to stay in GOP hands, Congress. Landrieu is one of four Senate Democrats seeking re-election in states Obama lost in 2012, so her political fortunes this year are among the nation's most closely watched.
In this race, allegiances don't fall neatly along party lines.
"I'm a die-hard Republican, but I love Mary Landrieu," said Lafayette resident Mark Miller, who owns and runs multiple Louisiana-based companies that drill and offer support services to other energy firms. "You can't overstate what it means for this state to have her experience and influence, especially with the energy chairmanship."
Among other things, Miller cites Landrieu's support for the Keystone Pipeline extension, her opposition to cap-and-trade legislation, her defense of offshore drilling after the Gulf oil spill and her support for the industry's tax advantages. Landrieu has also garnered support from shipbuilding magnate Donald "Boysie" Bollinger, noteworthy because Bollinger helped bankroll the GOP's takeover of the Louisiana Legislature.
But some of the senator's votes since Obama's inauguration — on health care and budget issues, in particular — are enough to drive erstwhile supporters to Cassidy, a congressman.
"Our civic responsibility has to shift this time to what's best for the nation," said Lafayette attorney Clay Allen, a Republican who said he backed Landrieu in 2008 based mostly on Louisiana's needs after Hurricanes Katrina and Rita. "In the intervening years," Allen explained, "I've just not seen her do the right thing on the debt, the deficit, health care — that's what voters here are most concerned about." He cast Landrieu as "hyper partisan," while Cassidy offers "more equanimity."
The GOP dynamic is more complicated than just being anti-Landrieu. There's an internal party struggle, as Cassidy faces skepticism about his conservative credentials due to his donations to Landrieu and other Democrats and, later, his push as a state senator for health-care exchanges that resemble some parts of the president's health care law.
And Louisiana's "jungle primary" — all candidates are on one November ballot — further complicates the Republican picture. Tea party challenger Rob Maness and at least one other candidate could block Cassidy from any hope of a first-round majority, meaning Landrieu either wins outright or advances to a December runoff against Cassidy.
In a recent interview with The Associated Press, Maness argued that Cassidy "is the wrong man" to hold Landrieu accountable on the Affordable Care Act.
Though it's her fourth Senate race, Landrieu has never exceeded 52.1 percent of the vote, and 2014 is a new scenario for her. She won her first re-election in 2002, also a mid-term year, but Republican President George W. Bush was popular among whites in Louisiana and she used her support of his tax cuts to demonstrate bipartisanship. She won a third term in 2008, but then-Sen. Obama's presidential bid helped maximize black voter turnout, particularly in her native New Orleans. This time, she has to navigate Obama's poor standing among white voters in Louisiana without him being on the ballot to excite black voters.
The high stakes ensure an expensive campaign involving more outside money than Landrieu has had to contend with before. Landrieu reported almost $6.4 million in her campaign account to start 2014, ahead of Cassidy's $4.2 million. But the congressman's 2013 fundraising was as strong as any Republican Senate challenger nationally, and each camp concedes that the other will have plenty of money between official accounts and independent PACs.
Americans for Prosperity, the national tea party group financed by the billionaire Koch brothers, has opened a state chapter here and already spent an estimated $600,000 on television advertising linking Landrieu to insurance policy cancellations under the Affordable Care Act.
Meanwhile, an independent Democratic group called the Senate Majority PAC released an ad lambasting Cassidy as "part of the problem in Washington" for, among other actions, a series of votes that helped lead to a partial government shutdown in October.
Predictably, both candidates forcefully frame their records in Washington in ways that fit into this year's electoral landscape.
Cassidy, who has often appeared on cable news as a GOP critic of the health care law, raised the issue this week in a telephone town hall for his congressional district. It wasn't an official campaign event, but Cassidy repeated the Republican promise to "repeal and replace" the law. He never mentioned Landrieu, but told listeners that "Harry Reid and the Democrats ... are serving as a rubber stamp" for Obama.
Landrieu, for her part, says she would vote for the Affordable Care Act again. But she's also supported delays of various provisions, including extending the deadline for individual to obtain insurance policies. More recently, she introduced a bill that would explicitly exempt existing individual policies from the new minimum coverage standards that led to the cancellations.
Follow Barrow on Twitter @BillBarrowAP.
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