I respect Bernie Sanders. I admire his passion and his devotion to the common good as he conceives it. I find his style of leftist politics — with greater ties to the class-focused concerns of the Old Left than to the cultural and identity obsessions of the New — quite compelling. I admire the democratic socialist welfare states of Northern Europe on which he models his own policy proposals and would be happy to see the United States move further in that direction.

But it isn't going to happen.

If you Feel the Bern, by all means keep fighting the good fight. Work to get Sanders and his issues placed front and center in the campaign. Act as if you think he has a good chance of burying Hillary Clinton, winning the Democratic nomination, and then triumphing over whichever candidate comes out on top at the end of the GOP primary scrum.

But facts are facts — and the fact is that Bernie Sanders is not going to be elected president of the United States.

The first obstacle Sanders faces is of course winning the Democratic Party's nominating contest against Hillary Clinton. At the moment Sanders and his supporters feel like they have a good shot because he's currently leading many polls in Iowa and New Hampshire. If he takes those first two states, showing that Clinton is beatable, then all bets are off.

Except that they're not.

For one thing, lily-white Iowa isn't especially representative, and neither is even more lily-white New Hampshire, which also just so happens to border Sanders' home state of Vermont. Once the voting moves on to states in the South, West, and Midwest, and to bigger, more demographically diverse states where vastly more delegates are at stake, Clinton is quite likely to come out on top over and over again.

How likely? Very. We know this because of the national polling spread. Clinton has led Sanders in every poll taken since the start of the election cycle. The most recent ones place Clinton in the lead by anywhere from 4 to 25 percentage points, with the RealClearPolitics polling average showing Clinton nearly 13 points ahead. When a candidate consistently comes out on top, she is winning.

But what about the 2008 scenario? That's when Barack Obama leapt ahead of Clinton in February after trailing her handily up to that point and ended up beating her to the nomination. That's obviously the script that Sanders supporters hope to see repeated this time around.

The problem is that Bernie Sanders isn't Barack Obama — and no, I'm not just talking about Obama's presumably much greater ability to mobilize the African-American vote. I also mean his enviable capacity to inspire moderates as well as liberals to vote for him. Sanders, by contrast, is the strong favorite of those who identify as "very liberal" but understandably polls weakly among self-described "moderate" Democrats. With Sanders continuing to propose very liberal economic policies that even leading progressive commentators consider to be vague and unrealistic, that is unlikely to change.

But doesn't Clinton face equal and opposite problems of her own by appealing primarily to moderates in the party? She would if there were equal numbers of economically liberal and moderate Democrats, but there aren't. Though the number of Democrats and Democratic-leaning independents willing to describe themselves as economically liberal has increased in recent years, the terms still apply to just 32 percent of the total. The proportion of those describing themselves as economically moderate or conservative, meanwhile, is 64 percent.

Which means that Clinton's more economically moderate base of support is roughly double the size of Sanders' liberal base.

To those, finally, who look to Donald Trump's remarkable ascent in the Republican primary field as a sign that a populist insurgent can overturn the preferences of party establishments, a note of caution is in order. Leaving aside the fact that, unlike Sanders, Trump has been leading in national polls for six months straight, and often by wide margins, there remains the complication that Trump's campaign scrambles established ideological assumptions on the right rather than simply reinforcing or radicalizing them. The mogul from Manhattan combines a far-right stance on immigration with economic positions that make him sound like a moderate Democrat. That's why his candidacy is so dangerous to the GOP: It threatens to tear apart the electoral coalition and ideological agenda that has more or less held the party together since Ronald Reagan was elected 36 years ago.

Sanders' candidacy threatens no such thing. It merely aims to pull his party further to the left — as Democrats have defined the left since 1972. Now if Sanders had responded to Clinton's very liberal latter-day stance on gun control by championing the rights of gun owners, or if he'd made other strategic moves to the right on social issues (on abortion or religious freedom, perhaps), then he might well have sowed Trumpean chaos among Democrats and ended up leapfrogging Clinton to the nomination. But as it is, Sanders is merely doing what ideologically doctrinaire primary candidates always do: working to radicalize and purify his party's already established ideological commitments.

That strategy will only win Sanders the nomination if the Democrats lurch quite a bit further leftward — or if some new (or old) scandal suddenly engulfs Hillary Clinton — in the coming weeks or months.

But in that unlikely (but not impossible) event, wouldn't Democratic nominee Sanders stand a very good chance of winning the presidency? Haven't a series of head-to-head polls shown that Sanders does well and in some cases even better than Clinton against the leading Republican candidates?

Yes they have, but those polls deserve to be taken with several grains of salt.

For one thing, these same polls also show Clinton in a dead-heat against the fading and transparently absurd sideshow candidacy of evangelical neurosurgeon Ben Carson. That's strong prima facie evidence that the poll results are driven to a significant extent by voter ignorance. Put Carson on a debate stage opposite Clinton, and his support would collapse rapidly and dramatically.

Perhaps even more far-fetched is the finding that Sanders would defeat Trump by a wider margin than Clinton. Clinton's hypothetical victory over Trump by a narrow 2.5 percentage points can be explained by the fact that both candidates would be appealing to the same bloc of white working-class voters, many of whom are Democrats. That could indeed make Clinton vulnerable against Trump. But to believe that Sanders would outperform her to beat Trump by 5.3 percentage points one has to presume that Sanders could do a better job than Clinton of persuading this (or some other) bloc of pro-Trump voters to support him instead.

Let's just say that I find that implausible. Americans as a whole are strongly disinclined to vote for a socialist — more disinclined than they are to vote for a Catholic, a woman, a black, a Hispanic, a Jew, a Mormon, a homosexual, a Muslim, or an atheist. Is it at all likely that white working-class would-be Trump supporters are among the country's most open-minded voters in this respect?

Sorry, I don't buy it — and neither should you.

Bernie Sanders is a good man and an effective advocate for the causes he champions. But he isn't going to be president.