In his announcement video, he appears with his wife, Laura, and both introduce themselves to supporters. He goes on to say that his run for Senate "is gonna be a tough race."

"I'm running against Senator Mary LandrieuMary LandrieuFive unanswered questions after Trump's upset victory Pavlich: O’Keefe a true journalist Trump’s implosion could cost GOP in Louisiana Senate race MORE, who's been there for 18 years, and against the most powerful man in the world, Barack ObamaBarack ObamaPresidential secrecy and transparency in the age of Trump The Obama presidency that never was Conway: ‘We would welcome a call’ from Lewis MORE. President Obama wants Senator Landrieu reelected," he says in the video.

Cassidy's effort to tie Landrieu to Obama reflects the president's deep unpopularity in the state. He lost in 2012 by more than 15 percentage points, and Republicans will look to weigh Landrieu down with Obama's baggage.

However, a recent survey showed that while President Obama remains unpopular in Louisiana, he's got a slightly higher approval rating than Louisiana Gov. Bobby Jindal (R). In that same poll, Landrieu is viewed favorably by 56 percent of respondents.

She'll still face a tough fight in 2014, and is considered one of Democrats' most vulnerable incumbents. 

But Cassidy, too, could face a challenge from the Right, as a handful of potential contenders have not yet ruled out a run.