(CNN) - As the Senate race in Louisiana draws closer, the state's GOP is trying to unite around one candidate: U.S. Rep. Bill Cassidy.
Cassidy, a doctor, is one of three Republican challengers trying to unseat three-term Democratic Sen. Mary Landrieu.
"If Louisiana goes Republican this fall, the Senate will go Republican - and Bill Cassidy is just the kind of conservative to make sure that happens. With a strong candidate like Dr. Cassidy and a united state party behind him, I have every confidence we will be successful this fall," said Republican Party of Louisiana Chairman Roger Villere in a statement.
The state's backing comes on the heels of endorsements from Texas Gov. Rick Perry and former House Speaker Newt Gingrich.
The most recent polling shows Landrieu facing a tough re-election, with support from just 42% of voters, according to the New York Times Upshot/Kaiser Family Foundation. While Cassidy trails at 18%, support for the two other GOP candidates - Paul Hollis and Rob Mannes - is in the single digits. A substantial number of voters had not made up their minds.
But there is no primary in Louisiana, so all the candidates appear on the November ballot. If a candidate does not win 50% of the vote, the top two candidates compete in a runoff in December.
As Landrieu continues to sink below the 50% mark, it seems more and more likely she and Cassidy will square off.
"The Louisiana Republican Party understands that now is the time to end Senator Landrieu's rubber stamp once and for all. I'm honored to have Chairman Villere and the party's support, and our campaign needs it. We need every extra ounce of elbow grease we can get to take on President Obama's Energy Chair and the liberal machine behind her," said Cassidy in a statement, referring to Landrieu.
The state's GOP has not endorsed a single candidate ahead of a runoff election since it threw its support behind Bobby Jindal in the 2007 governor's race, according to the group. The endorsement of Cassidy, which "came without opposition," gives his campaign access to state party resources and personnel, the group says.
–CNN's Conor Finnegan and Steve Brusk contributed to this report.