In the 224 years since we've started electing presidents--ranging from great Americans like Washington and Lincoln to war crinimals like Jackson and FDR--there's a somewhat alarming statistic. We've had 43 men serve as president (Cleveland gets counted twice in history books which is why they say 44), and in nine cases the president has left office (through death or resignation) mid-way through his term.
That's a better than 1 in 5 chance that the president you elect will leave office and their VP will take over. And that doesn't include cases where presidents came close to being removed from office (Andrew Johnson was one Senator's vote away from being removed) or nearly died in office (a few inches away and Ronald Reagan would have died mere months into his first term). So the choice of a Vice President is one that should be very serious and well-considered--it's an excellent chance that the person picked for VP will be running the Oval Office one day.
And that's when it gets scary. Say what you will about various incompetent or unscrupulous presidents--the Warren Hardings, the James Buchanans, the JFKs--they were for the most part better than the crop of VPs we've had over the years (some of whom managed to make it to the presidency). This list includes:
1) John Tyler, who did become president, and the only one not buried with U.S. honors because he happened to become an official in the Confederate government later on.
2) John Breckinridge, who later ran on the Southern Democratic ticket in 1860, then he too became a high ranking official for the Confederacy and had to flee the country after the Civil War.
3) James Calhoun, who didn't live to join the Confederacy but was the sort of father of secession and treason. Plus, he was a big booster of the disastrous War of 1812.
4) Aaron Burr, another treasonous scoundrel who only escaped prosecution because his conspiracy never got moving.
5) Eldridge Gerry, who brought us gerrymandering. Thank him for the fact that politicians now can choose their voters and not the other way around.
6) Schuyler Colfax, who was a total jerk.
7) Henry Wallace, who was completely duped by the Communists (though in his defense, he repented in the 1950s).
To be fair, we've also had some great men serve as VP--Jefferson, Teddy Roosevelt, John Adams--but it almost seems they were in that slot by accident. In fact, Jefferson and Adams both served as VP at a time that the VP was elected separately from the President (as in, not on the same ticket) and as for TR, he was a reluctant choice forced on then-President McKinley.
The problem is how VPs are chosen. No presidential candidate (or political party, back when the party's delegates had a say in the selection of the VP) has been able to see the VP selection as simply one of "this person would be a great president". Rather, the pick goes something like this: "is this person plausible enough as president that the voters won't laugh me out of the room?" and if you're John McCain you don't even ask yourself that question. If the answer is "yes" then the overriding question is "how will this person scare up a few more votes for me?" In the old days, it meant nominating a very rich man for VP, so they can help fund the campaign. These days, it's about appealing to a consituency that the presidential nominee needs--Sarah Palin was intended to help McCain with women, Al Gore was supposed to help Clinton burnish his Southern Moderate cred, Joe Biden was added to give Obama some humor. The problem is, if we manage to get a great Vice President, it'll be more by accident than by design. We always vote the top of the ticket, and just hope the bottom half isn't so awful it drags the entire ticket down.
How to fix this state of affairs, considering the high likelihood that a VP becomes a P? Repeal the 12th Amendment.