JACKSON, Tenn. (AP) — Herman Cain's improbable campaign for the presidency is all about momentum right now. He's riding the wave of recent polls that have catapulted him from an also-ran in the Republican race to the elite top tier.There are many reasons his bid could fade as quickly as it rose. He acknowledged Friday that he will trail former Massachusetts Gov. Mitt Romney and Texas Gov. Rick Perry significantly in fundraising. Cain has never held elected office and could wilt under the rigors of the campaign and its withering scrutiny.But Cain's moment is right now, and the former Godfather's pizza chief executive is marketing himself with practiced skill, banking on his charisma and the notion that the messenger is as important as the message.His everyman image is resonating.