Louisiana Rep. Bill Cassidy (R) may have missed his window for an easy path to challenging Sen. Mary LandrieuMary Loretta LandrieuSenate GOP rejects Trump’s call to go big on gun legislation Project Veritas at risk of losing fundraising license in New York, AG warns You want to recall John McCain? Good luck, it will be impossible MORE (D-La.) for a Senate seat the GOP believes is ripe for the picking in 2014. 

Cassidy is well-known to be preparing for a race, and recently signed up prominent Louisiana consultants Jason Herbert and Scott Hobbs to help. 

He's been traveling outside of his home district and reaching out to prominent donors in the state, one Cassidy aide said.

But Cassidy hasn't yet made a run official and Republicans say a contentious primary battle against other GOP contenders becomes more likely with every passing day.

A handful of other Louisiana Republicans — Rep. John FlemingJohn Calvin FlemingCoast Guard suspends search for missing Ohio plane Freedom Caucus member to bring up bill on impeaching IRS chief GOP seeks to make it 52 MORE, former Rep. Jeff Landry, Chas Roemer, the son of former GOP Gov. Buddy Roemer, and Lt. Gov. Jay Dardenne — have either confirmed their interest in the race, or are said to be looking closely at it.

None of them have taken the steps Cassidy has to prepare for a bid. But one unaligned GOP operative in the state said that as Cassidy dallies, “Fleming may be getting more serious about” making a bid for the Republican nomination. 

"The longer that it's drawn out and it takes people to get in the race, the more likely it'll happen" that Republicans face a potentially bruising battle to move past the initial vote, the operative said.

Landrieu remains one of the most vulnerable Democrats going into 2014.  She is running for reelection in a state that President Obama lost by more than 15 percentage points in 2012. 

Republicans in the state plan to make the president the centerpiece of their attacks on Landrieu. 

They’re looking to hang his healthcare reform law around her neck, to start. And they hope that some of aspects of the more progressive agenda Obama is pursuing in his second term — notably expanded gun control, and potential environmental regulations that affect oil production — could provide added nails in the coffin they’re looking to build around Landrieu.

But Republicans could see their prospects diminish if they’re unable to rally around a candidate and, as Cassidy waits to decide, that becomes more difficult.

Landry told The Hill that as Cassidy takes his time to prepare for a run, he's "absolutely" been seeing an increase in supporters urging him to run.

He said that "it's confusing for me, and I'm sure it's confusing for voters" that the candidate who has made it clearest he wants to run, Cassidy, hasn't yet entered the race.

"We can't continue down this merry-go-round forever," he said.

It's unclear why Cassidy has waited to announce; an aide said that he's hoping to have "all his ducks in a row" before he announces.

Jason Dore, executive director of the Louisiana Republican Party, said that Cassidy's timeline was likely more a reflection of his penchant for preparation rather than any lack of support.

"This isn't really out of character for him. They're very careful, they want to make sure they have everything lined up before they announce," Dore said.

Still, a recent poll indicated Dardenne would be the strongest candidate against Landrieu, and he has the experience running a statewide race any Senate candidate would need in 2014. 

Rep. Charles BoustanyCharles William BoustanyDems face hard choice for State of the Union response Americans worried about retirement should look to employee ownership Top Lobbyists 2017: Hired Guns MORE (R), who this week announced he won’t be running, also fared better than Cassidy against Landrieu, keeping her lead to six percentage points. Landrieu led Cassidy by 10 percentage points.

Cassidy is the least conservative of the three former and current members of Louisiana’s congressional delegation who are considering a run, measured by the Club for Growth's scorecard and National Journal's vote rankings.

Bernie Pinsonat, a well-connected Louisiana pollster who has worked for candidates in both parties, speculated that Cassidy's position as slightly more moderate than his colleagues could keep him out of the race.

"Time will tell. That may be one of the reasons Cassidy doesn't run. Maybe he gets bad feedback from the religious right or some of the more conservative groups," he said.

Pinsonat added, however, that all signs continue to point to a Cassidy candidacy.

Groups that typically back conservative challengers — the Club for Growth, Senate Conservatives Fund and FreedomWorks — are all currently staying out of the race, though the Club for Growth and FreedomWorks said they are monitoring the candidates.  

Their reluctance to express opposition outright indicates they may not ultimately have a problem with Cassidy's candidacy.

And John Cummins, a Cassidy spokesman, pushed back against the idea that the congressman may not be conservative enough.

"Dr. Cassidy has a record of common sense conservative reform that represents the views of his district and the entire state. Couple his record with his unique background as a doctor in Louisiana's charity hospital system and his vision of reform could be very compelling to Louisiana voters,” he said.

Unlike some other deep-red states, the grassroots wing of the party in Louisiana doesn’t hold sway over the establishment wing. That was in evidence when Landry, backed by the Tea Party,  lost to establishment-backed Boustany by a double-digit margin in last November’s election. 

And even if a rift emerges, Pinsonat said Obama’s reputation in the state might just be enough to rally the party around Cassidy, if he jumps in the race soon.