When Rep. Connie Mack (R-Fla.) decided to run for Senate last fall, the relief among Florida Republicans was palpable.

Congressman Connie Mack. (Paul Morigi/WIREIMAGE FOR SPOTLIGHT COMMUNIC)

Six months later, Republicans are grumbling about Mack’s underwhelming campaign, and state Chief Financial Officer Jeff Atwater is saying he might get into the race. A new poll of Florida insiders say it’s not too late for a new candidate?

What happened?

As always, it’s never one thing that leads a candidate to struggle. But, in conversations with a number of leading Florida Republican strategists they point to cockiness as Mack’s downfall — painting a picture of a candidate too confident to interact well with donors, activists or the press.

“The whole entitled sense of ‘Kiss the ring’ comes across in screaming clarity at every event,” said one experienced Florida strategist.

Here’s a look at where — and why — Mack has underwhelmed to date.

* Fundraising: Despite his connections and widespread support, Mack isn’t raising the sort of money most people expected he would. And, some Republicans say he hasn’t even really tried.

Mack has only slightly more cash than primary rival George LeMieux, a long-time ally of former governor Charlie Crist who was appointed to the Senate to keep the seat warm for his old boss. Crist left the GOP after falling behind Sen. Marco Rubio in the GOP primary in 2010.

It’s true that Mack hasn’t been in the race nearly as long as LeMieux. But getting into the race late, he was expected to raise funds at a faster pace. Nelson is sitting on a $9 million war chest; Mack has $1.3 million in the bank. 

* Tea party: Mack, some say, has ignored the grassroots. When he does pay attention to them, it’s not much better. At an Orlando tea party forum Mack called the budget proposed by Rep. Paul Ryan (R) a “joke.” When Orlando activists held a straw poll, Mack came in last. In all, he’s come in last in three consecutive straw polls. Mack campaign spokesman David James says the campaign was never told that two of those straw polls were taking place.

* Media: Mack’s campaign has picked unnecessary fights with the press, including one blast against the Tampa Bay Times over a snarky headline on a blog post.

“I’m wondering how a statewide campaign envisions its long-term relationship with the largest newspaper in the state after the campaign manager laid out such diatribe,” wrote the Orlando Sentinel’s Scott Powers.

While Mack has done himself no favors, LeMieux has done his part to make the going tough for him.

One LeMieux ad says Mack’s “only real job” was at Hooter’s. LeMieux compared his rival, who is divorced and once engaged in a bar fight, to Charlie Sheen.

There has been some backlash against LeMieux. One Republican state committeewoman sent a letter to fellow GOP leaders calling LeMieux’s tactics “embarrassing” and “a grave disappointment.” But LeMieux doesn’t have much to lose by continuing to go negative.

Mack’s campaign points out that he still leads his rivals in polls and cash. The influential American Conservative Union just endorsed Mack

“It’s really more about the fact that he hasnt been accessible and he hasn’t been that visible,” said Brad Coker, who runs the independent Mason-Dixon polling service. “Republicans aren't bailing on him, but they’re just concerned that he’s been a little too low-key.”

Even with Mack’s shortcomings, polls show a very close race. The most recent Quinnipiac poll has Nelson leading Mack by eight points, but the senator is still below 50 percent, and other surveys show an even tighter race . The shuttering of the NASA space shuttle program takes away one of his key strengths.

The Florida Senate primary isn’t until Aug. 14, meaning Mack has plenty of time to make up for his campaign’s failings to date. But, his initial months as a Senate candidate isn’t inspiring much confidence in party strategists who once saw Florida as a prime pickup opportunity.