Obama's support among Hispanics slipping?

This is based on Gallup "key indicators" weekly pooled data, the last of which ends Sept 21.  Obama's lead among Hispanics - according to Gallup - was down to +15% from +40% a month earlier.

Support among non-Hispanic Whites (Obama-McCain): 
Aug 18-24: 37-52 
Aug 25-31: 40-50 
Sept 1-7: 39-53 
Sept 8-14: 37-55 
Sept 15-21: 42-51 (M +9; best O-margin pre-last week) 
Support among non-Hispanic Blacks: 
Sept 8-14: 93-4 
Sept 15-21: 93-3 
Support among Hispanics: 
Aug 18-24: 58-31 
Aug 25-31: 64-24 (O +40) 
Sept 1-7: 60-31 (O +29) 
Sept 8-14: 55-35 (O +20) 
Sept 15-21: 53-38 (O +15; pre-last week; lowest O-margin)

I wonder why that is - Obama losing ground among Hispanics even as he gains among non-Hispanic Whites.

Recently, Obama's campaign put out the "Limbaugh" ad [clarification] [where Limbaugh's apparently attacking Mexicans].  Politifact says the ad came out on Sept 18, and called it "pantalones en fuego" wrong (also includes the video).  That ad also comes bang in the middle of that last week for which Gallup's pooled internals are available.

One way to read that ad is that Obama's support was slipping among Hispanics in their internal polling, and so they put out this misleading ad.  Another way is that somehow, Hispanics saw the ad, and figured Obama was trying to scare them... Much as an Obama-bot I am, and as we know McCain in trying to win the nomination said he wouldn't vote for his own immigration bill, yes, that ad was trying to scare Hispanics by linking Limbaugh and McCain, and I wish Obama hadn't put that out.  Still, looking at the Gallup trends (O+40 to O+15 in one month), the first explanation seems more reasonable... We'll see over the next couple weeks if it worked, though the effect may well be lost in the economic crisis effect -Hispanics are as effected by it as anybody else.

Of course, I still haven't figured out why Obama's losing ground among Hispanics in the first place...

[UPDATE: Yes, the dkos/R2K poll shows Obama up 40 points among Latinos, and had been for a while.  But (a) I am looking at Gallup which has a longer history; (b) Gallup's pooled weekly sample has about 7000 voters; say 15% Hispanics, makes that a Hispanic sample of ~1000 voters, with a MOE of 3%.]

As I was writing this, I looked up PPP's numbers for two states where Hispanics are influential - CO (O +7) and FL (O +3).  Obama leads CO Hispanics 57-36 (PDF), but McCain and Obama are almost even among FL Hispanics (including Cubans) (PDF).  Obama's gotta win them back...

I wrote this post at dkos first, here.  I got a lot of flames, including accusations that I was concern-trolling... That if I didn't know the difference between Florida and NM Hispanics, I shouldn't comment... While all I was doing was point out that based on the Gallup data, which have a decent sub-sample size in the pooled weekly data, Obama seemed to be slipping - which might be confirmed by the release of the "pants on fire"-wrong "Limbaugh" ad (as the Obama camp's reaction to try and bring back Latinos).  Guess I am not a complete Obama-bot after all - my support isn't blind.