There are at least a dozen realistic contenders for the Republican presidential nomination, including three senators, the former governors of Florida and Arkansas, the current House Budget Committee chairman and a gaggle of current governors (John Kasich in Ohio, Mike Pence in Indiana, Rick Snyder in Michigan, Scott Walker in Wisconsin, Rick Perry in Texas, Bobby Jindal in Louisiana).

The 2012 Republican Convention (J. Scott Applewhite/AP) The 2012 Republican National Convention (J. Scott Applewhite/Associated Press)

In addition to considerations about family, fundraising and economic sacrifice, potential candidates will need to decide whether they are ready to run. Maybe it is a quaint idea in the post-Herman Cain world to think presidential candidates should know things and have reasonable proposals to present to voters, but ultimately, the public will have to decide whether they can picture the candidate in the White House. As a not-quite-candidate, you can get away with platitudes, but as an actual candidate you’re going to be asked serious questions:

What would you do if Vladimir Putin invaded [fill in the name of a former Soviet state he has not grabbed by the time the campaign begins in earnest]?

How do you think economic growth can be accelerated?

Specifically, what is your plan to reform entitlements?

Where have you traveled overseas and what world leaders have you spoken with? What did you learn?

Are we spending too much or too little on defense? How much would you add or subtract, and what would it be used for?

Is it appropriate to collect metadata to protect the U.S. against terrorist attacks?

What do we do with the 11 million people in this country illegally?

Describe in detail your alternative to Obamacare.

Provided Iran doesn’t already have the bomb, what would you do to prevent that from happening?

If Congress won’t repeal Obamacare or pass immigration reform, what would you do?

Did the Supreme Court decide the Voting Rights Act case correctly? Why or why not?

What role do states have in immigration and energy regulation?

What causes poverty? How do we reduce it?

These and other queries aren’t “gotcha” questions, but they do require some thoughtfulness, command of the facts and creativity. A potential candidate who doesn’t already know what he would say (and respond to some detailed follow-ups) and isn’t already assembling people to help answer them will find it tough sledding in a presidential race. (And, of course, there are many variations on these and other equally weighty topics.) Generic answers (“I’ve been a governor” or “I believe in freedom“) aren’t going to wash. It is noteworthy that, as The Post’s Glenn Kessler documented in his book, George W. Bush, a sitting governor who had observed his father’s presidency close up, was at this point in the cycle already scouting out his team and beginning introductory meetings. He was then prepared for in-depth policy briefings in Austin in January 1999 (2015, in terms of this cycle).

Certainly, running for president isn’t only about what you know. It is also about conveying why the country needs you — your character, background and talents — and not one of the other accomplished candidates. The undertaking requires a modicum of self-awareness. A candidate has to seriously consider: Will my family and I have the stamina and the emotional toughness to take whatever is thrown our way? Will I be overwhelmed by the job? Can I really galvanize a room of Republicans, an entire party and, ultimately, the country? Do I have flaws serious enough to embarrass my supporters and undermine my prospects in the general election?

While there are, as I noted, a dozen or so people potentially looking seriously at a race in 2016, I would that argue very few actually know what they need to know, can put together a top-flight organization, can endure scrutiny and can have that presidential aura we expect from the chief executive. An experienced Republican wisecracked that when the candidate enters the room, he has to be the guy people say “Wow! There’s a future president” and not come across as the Midwest sales manager for a big company.

Republicans put such reliance on ideology that they are surprised when lack of basic knowledge, competence, the ability to connect with regular people and other personal factors thwart ideologically “correct” candidates’ ambitions. They shouldn’t ignore the experience of President Obama, as Peter Wehner points out:

By now, nearly five and a half years into the Obama presidency, objective people can draw reasonable conclusions, among which are these: Barack Obama was among the least prepared men to ever serve as presidency. It shows. He has been overmatched by events right from the start. He is an excellent campaigner but unusually inept when it comes to governing. By temperament and experience, based on skill set and ability, Mr. Obama is much better equipped to be a community organizer than to be president of the United States.

If a GOP nominee is no better prepared than Obama, the party and potentially the country will be in trouble.

To be blunt, I’m not yet sure those most likely to run have all the necessary qualities not only to win but also to govern effectively. Some have a few of the necessary characteristics, while others have different ones. What is needed is someone who has the complete package. There is a climb for most of the most frequently mentioned candidates to get to the level they will need to be at in order to compete seriously. They better start climbing now if they want to be credible contenders.