This presidential race has been weird in a number of ways, but one of the weirdest is that successful outsider insurgents who have a real shot at their parties' nominations have barely been attacked at all.

Donald Trump has hurled endless insults at his competitors and the GOP, without receiving much in the way of coordinated return fire. The other candidates just keep attacking each other. Jeb made a few attempts at taking on Trump, but Trump swatted them away like a lion with a ball of yarn. Only National Review even put any serious effort into it.

Meanwhile, the left insurgent candidate, Bernie Sanders, has also had a mostly free ride.

If you say something like this on social media, you'll be beset by furious Sanders supporters. (If there's one thing it's easy to do on social media, it's get yourself beset by furious Sanders supporters.) But it remains true that Sanders has faced very few serious attacks.

Most attacks on Sanders so far are relatively mild

His supporters will deny it and cite the following:

Clinton has accused him of being inconsistent on gun control.

Clinton has accused him of a lack of practical wisdom for wanting to start health care reform all over again rather than building on the successes of Obamacare.

Clinton surrogate Claire McCaskill (and others) have argued that a self-declared socialist can't win as president in key swing states.

Paul Krugman and others have argued that Sanders and his supporters have a somewhat naive theory of political change.

I have no interest in litigating any of these attacks here. Like any Democrat elected president in 2016, Sanders wouldn't be able to get much done, but he would block attempts to roll back Obama's accomplishments and have a chance to fill a few Supreme Court vacancies.

When Sanders supporters discuss these attacks, though, they do so in tones of barely contained outrage, as though it is simply disgusting what they have to put up with. Questioning the practical achievability of single-payer health care. Impugning the broad electoral appeal of socialism. Is nothing sacred?

But c'mon. This stuff is patty-cakes compared with the brutalization he would face at the hands of the right in a general election.

His supporters would need to recalibrate their umbrage-o-meters in a serious way.

Conservatives are very good at attacking liberals

In a sense, this seems so obvious to me that it feels peculiar to argue for it. But Sanders supporters do not give the impression that they are cognizant of Sander's vulnerabilities.

Partly this is because the GOP has been very careful so far not to go after Sanders. They show every indication of preferring him as an opponent, so they have no reason to hurt his chances in the primary.

But if he wins, they will rain down fire.

And the organs of the right will feel absolutely no obligation to be fair. They're not going to be saying, like Sanders's Democratic critics, "Aw, Bernie, you dreamer."

They're going to be digging through his trash, investigating known associates, rifling through legal records.

They're going to ask struggling middle-class workers how they feel about a trillion dollars in new taxes to fund a grand socialist scheme to take away everyone's health care insurance and hand them over to government doctors.

They're going to ask when he stopped being a communist, and when he objects that he was never a communist they're going to ask why he's so defensive about his communist past, why he's so eager to avoid the questions that have been raised, the questions that people are talking about.

And when Sanders and his supporters splutter that it's inaccurate and unjust and outrageous, the right will not give a single fuck.

Sanders has some pretty glaring vulnerabilities

I'm not sure I have the requisite killer instinct to fully imagine how the GOP will play a Sanders campaign. But consider just this low-hanging fruit:

Sanders would be the oldest president ever to take office — older than John McCain, who faced serious questions about this in 2008.

Sanders is a socialist. "No, no," you explain, "it's democratic socialist, like in Denmark." I'm sure GOP attack ads will take that distinction into careful consideration.

Sanders explicitly wants to raise taxes, and not only on the rich.

That's just the obvious stuff. And he has barely been hit on any of it so far.

I have no real way of knowing whether Sanders and his advisers appreciate what's coming if he wins the nomination, or whether they have a serious plan to deal with it, something beyond hoping a political revolution will drown it out.

But at least based on my experience, the Bernie legions are not prepared. They seem convinced that the white working class would rally to the flag of democratic socialism. And they are in a state of perpetual umbrage that Sanders isn't receiving the respect he's due, that he's facing even mild attacks from Clinton's camp.

If they are aware that it's been patty-cakes so far, that much, much worse and more vicious attacks are inevitable, and that no one knows how Sanders might perform with a giant political machine working to define him as an unhinged leftist, they hide it well.

In the name of diverting some small percentage of the social media bile surely headed my way, let's be clear about a few things: This is not an argument against supporting Sanders. There's nothing dumber than making political decisions based on how the other side might react. (For one thing, that would have foreclosed supporting Obama, a black urbanite with a funny name, in 2008.)

But it is an argument that Sanders has gaping vulnerabilities that have not yet been exploited at all, so his followers should not yet feel sanguine about his ability to endure conservative attacks. Also they should get a thicker skin, quick.

And, yes, of course Hillary Clinton will be attacked too. The conservative movement's hatred of her is rightly legendary.

The difference is that no one in American life has been attacked more, for longer, than Clinton. She has taken almost continuous fire, from the right and the media, from the moment she emerged into public life.

All the attacks — her alleged inauthenticity and untrustworthiness, her connection to her husband's sexual misdeeds, her fealty to Wall Street, her sloppy paperwork (from Travelgate to emails) — have been made, again and again. She has survived them, again and again, and remains extremely popular with Democrats.

This is not to say that these rehashed attacks can never work, or that Clinton can't be successfully tarred this time around. They've already driven her unfavorables pretty high.

But if there's one thing people can know for certain about Clinton, it's that she's resilient in the face of attack.

As Sanders edges closer to the once-unthinkable, winning the Democratic primary, it would benefit him and his followers to start thinking and preparing now for attacks that are inevitably going to be uglier and more vicious than anyone now imagines.