The President of the US is a very prominent role (perhaps too prominent), but the Vice President (VP) is less important. However, the position is a very interesting one that has changed substantially over time, and is worth exploring.
The writers of the Constitution were concerned that the Electoral College members would be tempted to vote only for someone from their own state, and not for the good of the country. Thus electors were given two votes, with the hope that they would look more widely, and the VP was the second-highest vote getter (where this does not lead to an unambiguous winner, the House and/or Senate makes the decision). This system was overhauled quickly: after the emergence of political parties, the President and VP ended up being from different parties (in 1796) or from the same party but tied (1800). The Twelfth Amendment of 1804 specified that electors must vote for the two offices separately, and tightened up a few other areas.
The VP has always had the role as presiding officer of the Senate, and can cast a tie-breaking vote. They also have the right to preside over impeachment trials of federal officers (except the President, for reasons of conflict of interest), although it is unclear what would happen if the VP were impeached (this has never happened). The VP also presides over electoral vote counts (which played a big part in the attempts to subvert the 2020 election).
The Constitution specifies that the VP acts as President where necessary, but not that the VP actually takes over as President (if the current one dies, for example). The first time this became important was in 1841, and the practice established then of actually taking over as President has persisted (being codified only in 1967 with the 25th Amendment). Overall, 9 VPs have ascended to the Presidency, whereas only 4 sitting and 2 former VPs have been elected President (I am not discussing being re-elected after ascending, which has its own wrinkles owing to the 22nd Amendment of 1951 – no ). Overall, being Vice President is a reasonably good stepping stone to President. Daniel Webster was twice offered the role of VP and declined – both of the offerers died in office, and Webster never became President! However, of the 49 VPs so far, 7 have died in office and 2 resigned, which is a higher rate of dropout than for Presidents.
For over a century, the VP was considered a rather pointless position, and there are many examples of VPs complaining about this fact. Interestingly, there was no process for replacing a VP who ascended or dropped out until the 25th Amendment was ratified, and the office was vacant for almost 20% of the history of the republic until then. During the first few half of the 20th century the VP gradually became more powerful, being made a member of the Cabinet and recipient of National Security briefings. It seems almost incredible that Harry Truman, who held the office for close to 3 months before taking over after Roosevelt’s death, did not know of the Manhattan Project until he became President!
In the following few decades the VP was given an office in the White House. The role has continued to expand, and modern VPs act as policy advisers, take over various ceremonial duties, liaise with Congress (which makes sense given the unique dual role in the executive and legislative branches), etc. Allegedly there has been an increase in the quality of VP candidates, and certainly the selection process is more influenced by the presidential candidate than in the past, which one would expect would lead to a better working relationship between President and VP.
After this long evolution, the role of VP is clearly an important one. It makes sense to consider the VP candidate (“running mate”) very seriously when deciding on whom to vote for for President. Ballots usually list both candidates and voters vote for both or neither of them, so they are to be considered as a package deal. If the President-elect drops out before being sworn in, the VP-elect takes over. I am surprised that I have never seen a TV show or movie where the VP-elect pressures the more popular President-elect to step down for “health reasons” or assassinates them (I do know about House of Cards).
Given this importance, I think that there should be more scrutiny of VP candidates, and we should create a scorecard for them, which will be a little different from that for President. The skills required for the two jobs are similar enough, however, that big changes to the scorecard should not be necessary.