Hillary Clinton is still very far ahead in the 2016 Democratic primary, but she's also had one ace up her sleeve should any challenger get within striking distance: electability. She may not inspire the enthusiasm of Bernie Sanders or Donald Trump, but she's got the moderate record and lengthy experience that would make her a strong general election choice.

That argument has come into question of late, however. Hillary is sliding in the polls. Her favorability numbers have fallen from about +8 to -10. And she's doing surprisingly poorly in head-to-head election matchups against Republicans — most shockingly, losing to Trump by five points in a recent poll.

All this raises the question: Would Hillary Clinton actually perform that much better than Sanders (or another challenger) in a general election? There are good reasons to suspect not.

To be sure, a great deal of Clinton's poor performance of late is likely due to blatantly unfair treatment from the mainstream media. We're now several weeks into wall-to-wall coverage of Clinton's email server thing, and there is still no hint that this supposed controversy is anything more than a minor bureaucratic foul-up. Indeed, we don't have any clear sense of what the story is even about. Just as it did during her husband's administration, the press is covering an untied shoelace like it's the Teapot Dome, while all but ignoring other egregious lapses in her judgment.

Unfortunately for Clinton, the capering Very Serious People in the political press aren't going to quit their jobs to learn why austerity at a time of high unemployment is bad. And she doesn't have the charisma to win people back by main force. I'm afraid she's stuck with the Clinton Rules.

Of course, if Sanders were the frontrunner, he would face some obstacles as well. He's not nearly as well-known as Clinton, and doesn't have half the money that is flowing into her war chest. His principled stances and his honest approach to politics have given him a credibility boost — he continues to hold by far the biggest rallies of any candidate in either party — but these attributes would also make him more vulnerable to negative advertising.

So both candidates have some pluses and minuses. Sanders is a straight shooter and sparks huge enthusiasm, but he's unusually left-wing for an American. Clinton is extremely well-known and has endured years in the spotlight, but is a fairly wooden campaigner who is constantly dogged by faux-scandal.

But their respective political disadvantages would be sanded down the moment one of them sealed the Democratic Party nomination. Activists and loyal Democrats would quickly realize that either Sanders or Clinton would be miles better than any Republican, and they would all fall in line. Wealthy liberals would remember that when it comes to domestic policy, Congress is where the action is — President Sanders, after all, couldn't pass his large tax increases by himself.

For both Republicans and Democrats, the party is mostly what matters, politically speaking — not the identity of individual candidates. Positions are chosen and policies are made through a process involving a very large number of people, from the individual voters on up to representatives, senators, party elites, and eventually the presidential candidates. The difference between any two Democratic presidents is going to be relatively tiny compared to that between a Democrat and a Republican.

That's not to say that there would be no difference between a Clinton administration and a Sanders administration. A great deal of policy these days is effectively made through executive branch rules, and on foreign policy presidents have basically a free hand. But even there, the executive branch is a big, complicated mechanism that is difficult to change, particularly the vast Pentagon bureaucracy. While I have no doubt that Sanders would generally make better decisions as commander-in-chief, particularly with regard to the use of force, Clinton would likely be much better at the backroom deal-making and the persuasion of global elites that comprise a large part of diplomacy.

So as far as the primary is concerned, Clinton better not rely on her supposed electability. Better to just win on the merits.