04:08 - Source: CNN
Senate showdown just six weeks away

Story highlights

A new CNN poll shows the Louisiana Senate race is very close

Sen. Mary Landrieu leads her GOP challenger by only three points

Gap is within the poll's sampling error

If no candidate gets more than 50% in November, there's a runoff

Washington CNN —  

As Democratic Sen. Mary Landrieu defends her U.S. Senate seat in Louisiana, a new CNN/ORC International poll indicates the third-term incumbent carries a slim advantage over her closest GOP rival in the general election this November.

But this is Louisiana, and the election system can be complicated. There are nine candidates – Republicans, Democrats, and a Libertarian – on the ballot this November, and if no candidate crosses the 50% threshold, the race moves into a December runoff between the top two contenders.

Landrieu currently falls well below the 50% mark at 43% support among likely voters. Republican Rep. Bill Cassidy comes in second at 40%, according to the survey.

But the poll’s sampling error among likely voters is plus or minus four percentage points, meaning the two candidates are about even.

In a state with large swaths of conservative voters, Landrieu is considered one of the most vulnerable Democrats up for re-election this year. Republicans, eager to take control of the Senate, have focused on the race as a potential pick-up seat. The GOP needs a net gain of six seats to retake the majority.

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If the horse race in Louisiana stays relatively the same, Landrieu and Cassidy would be the two candidates heading into the runoff – and that’s when things flip.

The poll indicates that Cassidy would fare slightly better in a runoff than Landrieu, 50%-47%.

“Keep in mind that the electorate in December is probably going to be smaller and quite a bit different from those who turn out to vote in November,” CNN Polling Director Keating Holland said.

But the poll’s likely voter model can only estimate the November electorate, he added, and turnout is going to be extremely important in December.

“Landrieu wins a majority in a two-way race among all registered voters, but we know that only a small fraction of them will come out for a runoff,” he said.

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In her re-election bid, Landrieu has been touting her position as chairwoman of the Senate Energy and Natural Resources committee as a boon to her oil-rich state.

Like many Democrats in tight re-election bids from reddish states, Landrieu has also kept President Barack Obama at arm’s length due to his low approval ratings. The CNN/ORC poll shows that only 40% of Louisiana voters approve of the job Obama is doing in office. Instead, she has been selling a bipartisan record of working across the aisle and voting independent of her party.

But Landrieu has faced a slew of negative headlines this fall, including questions about her residency and improper uses of taxpayer-funded travel. And Republicans, including Cassidy, seized on a recent photo showing Landrieu helping a Louisiana State University fan perform a keg stand during a tailgate party.

Cassidy, however, is seeking to paint Landrieu as a rubber stamp for Obama. And as a physician and a three-term congressman who was a vocal opponent of Obamacare, Cassidy is trying make health care reform a big issue in the race.

As the incumbent, Landrieu has a large fundraising advantage over Cassidy, having brought in $14 million compared to Cassidy’s $8.6 million, according to the Center for Responsive Politics.

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Democratic outside groups have invested heavily in the race, spending nearly six times the amount Republicans have spent in opposition.

According to the poll, Landrieu does extremely well in urban areas and carries 85% of the non-white population but gets clobbered in the suburban parts of Louisiana.

Interestingly, women only slightly back Landrieu more than men, 48%-45% – a departure from polls that generally show incumbent Democratic women with a wider gender gap that can prove favorably in the voting booth.

The poll was conducted for CNN by ORC International by telephone with 1,013 adult Americans on September 22-25.