Vice President Joe Biden was back on the campaign trail Saturday, stumping in Louisiana for Sen. Mary Landrieu.
Landrieu, a Democrat in red Louisiana, could face an uphill battle for a fourth term in 2014.
Three non-partisan political race watchers describe the campaign as close.
The Cook Political Report says it leans Democratic; Capitol Hill newspaper Roll Call assesses it as a toss-up between the parties; and the Rothenberg Political Report scores the race as "Toss-up/Tilt Democrat."
Landrieu is considered a conservative Democrat. Recently, she and the state's other senator, Republican David Vitter, called for President Barack Obama to sign off on the Keystone XL pipeline that stretches from Canada to the Gulf Coast region. The pipeline project has broad Republican support but is generally met with more skepticism from Democrats and environmental groups.
The Louisiana Republican Party used Biden's visit to stir the waters ahead of the 2014 midterm election. It first called on Landrieu to call off the event because of Biden's recent remarks on gun control, then urged Landrieu to confront Biden over forgiveness for Hurricane Katrina loans.
"Mary Landrieu is the 'Last Liberal Standing' in Louisiana, so now she has to bring in liberals from other states to help her campaign," party chairman Roger Villere said in a statement.
The New Orleans Times-Picayune reported that Biden would headline a fundraiser for Landrieu at which ticket prices ranged from $250 to $2,500.
Her likely challengers include three Republicans: former U.S. Rep. Jeff Landry and U.S. Reps. Bill Cassidy and John Fleming.