As much as I'd like to see a regular person suddenly become President, it ain't gonna to happen. For all practical purposes, the record shows that you must be a Senator or a Governor before being elected as President.
I looked at the biographies of all presidents since Benjamin Harrison, and there are only five exceptions to the Governor or Senator rule:
(1) George H.W. Bush - Director of CIA, Ambassador to U.N.
(2) Gerald Ford - Minority Leader of the House
(3) Dwight D. Eisenhower - general/war hero
(4) Herbert Hoover - Commerce Secretary
(5) William Howard Taft - Secretary of War
The last three were all well known high level public servants before running for President. Ford never actually got elected to the job. Bush ran for the Senate twice and lost. He was lucky to be appointed Vice President, otherwise he never would have won the party primary.
If Jeffrey Sachs were serious about running for President he wouldn't be running for President at all; he'd be running for Governor or Senator.
[*** This post has been edited because for some reason I thought George H.W. Bush was a Senator and I left him off the list of exceptions. Sorry. ***]