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

The 2016 presidential contenders are already jostling, and hard-line conservative pundits are already measuring the ideological purity of each candidate. It’s very early in the game (too early to engage in silly evaluations about “front-runners”), but we can spot some telltale signs of danger for primary voters. By danger, I mean globbing onto a candidate who is unelectable and would lead the party off a cliff.

If a candidate refers to himself as a “real conservative,” run the other way. He’s interested in ideological puffery, not winning elections.

If he spends time bashing George W. Bush, forget him. He’s stuck in the past and likely doesn’t know (or care to know) actual facts about Bush’s actual record.

If he talks about “nation building at home,” he’s insulting your intelligence and insulting America, which doesn’t need to build a nation. (Fix the government is more like it.)

If he says the GOP’s problem is that we haven’t had people “unafraid” to articulate a conservative message, he’s delusional — or thinks you are.

If he spends time bashing the media, he’s a loser. Voters ultimately don’t care about the media, and he’s likely ill-equipped to deal with the national press corps.

If he derides experience, he’s not leveling with you. The current president lacked executive and foreign policy experience, and look where it got us.

If he says he’ll end Obamacare but doesn’t come up with an alternative, forget him. The Dems will eat him alive in the general election.

If he praises “self-deportation” and considers an earned path to citizenship to be “amnesty,” look for someone else. He hasn’t learned from the past and has thrown away a good chunk of the electorate.

If he promises a constitutional amendment to end gay marriage, go ahead and laugh. That’s just nuts.

And if he does all these things? Well, that’s a recipe for a Goldwater-type defeat if he’s the nominee.

Jennifer Rubin writes the Right Turn blog for The Post, offering reported opinion from a conservative perspective.