Any citizens can be a great president. However, today, there are two major challenges facing us.
We have a war in progress and the president was never a field commander in any capacity. This limits his ability to make accurate strategic decisions. He has to rely upon numbers of military advisers many of whom differ in how to run a war. Adolph Hitler ran into the same challenges even though he was previously a battlefield corporal having been awarded the iron cross, and the results of his strategic leadership are with us to the present day.
We have enormous legal challenges facing us. We are cutting back on constitutional safeguards in a way never seen before in our nation's history. The current president declared the constitution to be a "god damned piece of paper". A president with a legal background would understand better that when one defends constitutional safeguards, one can build a better case against the genuine trespasser. That is to say that failing to follow the constitution yields too broad a net that catches the innocent. The innocent then retaliate and you have enemies on two fronts: the outside and the inside.
I hope that answered the question somewhat. No mix of skills is perfect, but at a minimum today, we need a soldier/marine/sailor/airman - legally savvy candidate, in my opinion.
One of George Bush's biggest weaknesses is his lack of a legal mind.
Lawyers deal with the truth differently than anyone else. Maybe he would not have gotten into a war using allegations of weapons of mass destruction if he had known how to sift through evidence.
Maybe he would not have allowed the abuses at Abu Graib and Guantanamo if he truely believed in our Constitution and knew what that meant for the accused.
Maybe he would not have pursued a complete revision of the Bankruptcy Code solely benefitting the VISA banks if he knew what it would lead to for consumers and then the economy.
Maybe he would not have gotten into trouble firing his U S Attorneys.
I am a lifelong Republican, but I think Barack Obama will not have issues like these.
Legal training is valuable in many situations. That is why Presidents select attorneys to advise them on legal matters and implications. Attorneys should be free to give their honest advice and proceed to do so. Then the client, in this case the President, must weigh that legal advice along with other appropriate advice and make a decision. My preference is a President with strong experience, a history of considering diverse views, good judgment and proven integrity. Presidential candidates should disclose past activities and affiliations in order that he/she may be honestly evaluated by the electorate. Without full disclosure, the inference of hiding negative traits and deeds must be drawn. Since the Presidency is an executive position, not a legal position, I believe that a legal background is a neutral factor.