At dinner the other night, the subject of Maine’s Democratic caucus came up.

My friends were all middle-aged Democrats (I know – shocking, right?), and the question was who they would support on March 8, Hillary Clinton or Bernie Sanders.

“I want to caucus for Bernie,” one friend said. “But by that time I hope it’s a futile gesture.”

I knew just what he meant.

Once again, the nominating contest for Democrats is coming down to a choice between doing what your heart tells you is right versus doing what your head tells you is smart.

Sanders is right: The system is rigged, with the millionaires and billionaires growing more prosperous while the middle class and working class stagnate. Big money in politics has made the concerns of the rich top priorities, and government only works for the ones who can pay.

But following your heart can be risky. When you start thinking about Ted Cruz or Donald Trump naming the next three Supreme Court justices, the righteous feelings start to fade.

So the question for Democrats who are scared that a socialist from Vermont can’t win in November becomes not who you want to be president, or even who best reflects your values. It’s whether Hillary Clinton would be good enough. And while making that kind of choice doesn’t feel good, it’s what Democrats usually do.

Contrary to what Rush Limbaugh says, the Democrats are not a cabal of crazy left-wingers. Since they invented the modern nominating system after the nightmare of 1968, Democrats have gone with their hearts over their heads just twice: Barack Obama in 2008 and George McGovern in 1972. And you know what happened then.

Every other time, the “head” candidate beat the “heart” candidate, with the party nominating Jimmy Carter over Ted Kennedy, Fritz Mondale over Gary Hart, Mike Dukakis over Jesse Jackson, Bill Clinton over Jerry Brown, Al Gore over Bill Bradley and John Kerry over Howard Dean.

(I’m leaving out 1976, because after Vietnam and Watergate who can tell what anybody was thinking?)

In another time, Hillary Clinton would be the “heart” candidate. The potential first woman nominee of a major party should be producing the same kind of emotional response that the first African-American nominee inspired eight years ago.

But we already know her too well for that. What makes her the most electable candidate is that we know she doesn’t want to remake the system; she wants to make it better. She is the most electable candidate because she has something Sanders would never have – the blessing of the ruling class. She won’t be their first choice, but she’ll do, and Wall Street money will be there for her when she needs it.

Using questions of electability to decide who to vote for is the kind of calculation that makes Sanders voters furious. But it’s what Democrats almost always do. It’s not a revolutionary organization, after all.

Iowa had the opportunity to settle this.

A solid win for Clinton, such as the one predicted by the Des Moines Register poll last weekend, would have just about put an end to any serious threat against her front-runner status and would have made the rest of the race something close to a formality.

Even a narrow win for Sanders would have shown that she was vulnerable – not because she lacked money or powerful friends, but because she could not plausibly promise the fundamental change to the system that struggling people are demanding.

A squeaker doesn’t say much, either way. Clinton failed to cement her status, and Sanders has one less opportunity to make his claim.

The most telling result Monday was not the final vote tally, but the information about who voted. When you look at the ages of Iowa caucus attendees and who they supported, this was not a close race at all, but a landslide – if a landslide can go two ways.

Voters under 30 preferred Sanders over Clinton by 84 percent to 14 percent. Voters ages 30 to 44 also went for Sanders by a sizable margin, 58-37 percent.

But when you got past age 45, the numbers flipped. Voters ages 45 to 64 preferred Clinton by 58-35 percent, and voters 65 and older supported Clinton 69-26 percent.

My head tells me that means she will be the nominee because our system favors the old over the young, continuity over revolution.

But my heart tells me it’s the young voices that Democrats should be listening to, not the logic that gave them the Carter-Mondale-Dukakis treadmill of “smart” choices.

It also tells me that this will still be an agonizing choice when March 6 rolls around.