Herman Cain’s endorsement provided a temporary jolt for House Speaker Newt Gingrich’s struggling campaign, but Cain won’t help him Gingrich Florida — or really anywhere else.

The reason is simple: Gingrich is already winning the kind of Republicans that Cain appeals to. Throughout his campaign, polls showed Cain performing particularly well among Republicans who identify themselves as Tea Party supporters. And in interviews with Republicans in Iowa and Florida last year, I found conservatives liked that Cain both attacked President Obama aggressively and defended the Tea Party from the charge of it being racist.

But Gingrich is in many ways already the Tea Party candidate. In an NBC News/Marist poll of Florida voters released over the weekend, Gingrich narrowly leads Romney among Tea Party Republicans and those who themselves very conservative.

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National polls show the same trend: Gingrich dominates among Southern, conservative and Tea Party Republicans, the core of Cain’s appeal earlier in the election cycle.

Gingrich has two major problems. One, he badly trails among Republican moderates and in some polls, women, two groups where it’s not clear Cain has any particular sway.

The second is money, as Romney has vastly outspent Gingrich in Florida and could use his fundraising advantage in other states. Cain showed little ability to raise major amounts of money for his own campaign and is unlikely to help Gingrich much in that regard either.

Cain’s backing did provide Gingrich a bit of positive media attention after the former House Speaker had several lackluster debate performances. But that attention is likely to be gone if Gingrich sustains a double-digit loss in Florida, as current polls suggest he will.

Follow Perry Bacon Jr. on Twitter at @perrybaconjr