With talks of the vice-presidential choices getting louder, every aspect from the ethics of picking a running mate to the potential political boost of each potential pick, has its place in the discussion.
Historically nine VPs have succeeded the president, so the nominees must think seriously whether a would-be number two could successfully serve as number one. Keeping that in mind, other concerns should be on the candidates' brains like: who can help me win; who will complement me the best; and who would be best for the nation.
And perhaps more than other years, this election's VP nominees could have a deciding impact. Because the candidates themselves are so different, the VP choice could fatefully decide whether McCain's age comes off as experience or failed policies, or whether Obama's newcomer status translates to welcomed change or inexperience.