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 Loretta LandrieuLandrieu dynasty faces a pause in Louisiana Senate GOP rejects Trump’s call to go big on gun legislation Project Veritas at risk of losing fundraising license in New York, AG warns MORE, who's been there for 18 years, and against the most powerful man in the world, Barack ObamaBarack Hussein ObamaTrump: Police 'have every right' to protest Chicago mayor To woo black voters in Georgia, Dems need to change their course of action 2018 midterms: The blue wave or a red dawn? 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.