I don't know that they really care. If they did, they would have demanded to know who or what Obama is in 2008. What they wanted was "Change". They seem unhappy because they were not careful to specify that the "change" they wanted was change for the better, not change for worse.
(It would be convenient to think that there is some coordination between Trump and Romney's campaign -- but I doubt it. Trump doesn't need any encouragement to do what he does!)
Arpaio's press conference is on Tuesday. That could start the move by Romney surrogates to demand a full investigation of Obama and his background. The failure of the MSM to vet Obama in 2008 and McCain's lack of interest in pursuing the issue, should provide Romney with fertile ground to explore. Poll after poll show that the public is very skeptical about Obama's religion, his birth certificate, past associations with the likes of Ayers, Wright, etc.
Trump showed how easy it was to smoke Obama out and force him thru public pressure to respond to the birth certificate issue. And Obama provided a clearly fraudulent one. So now let's go after Obama's personal narrative. The Mariness biography unwittingly gave us lots of weapons to go after Obama the liar and fabulist.