No statute of limitations for murder.
Can someone come from a shady place and achieve things for themself? Sure they can. Harry Truman came out of the Prendergast machine and spent years establishing his credibility. Truman was fiercly partisan but personally clean. Prendegast knew that and made sure everyone else knew it also. Americans love that story, think of Manhattan Melodrama or James Cagney in G Men.

James ‘Brick’ Davis: I’m leaving tomorrow morning. That puts me on the other side of the fence than you, Mac.
‘Mac’ McKay, aka Joseph Lynch: That’s where you ought to be.
James ‘Brick’ Davis: Yes, but they’re out to get you. You and everybody else in your racket. And if they assign me to go after you, I’ve got to use everything I know about you.
‘Mac’ McKay, aka Joseph Lynch: You’ve got to play ball with them, Brick. Go to it.

The problem with Obama is that he has no meaningful record beyond his association with Ayers and Rezco and Wright. The ugly wound under the media gauze is all there is. So yes we will keep picking at it. That is what media do in a free society.