They were putting on a happy face Tuesday night at the postprimary election party for state Senate candidate Scott Wiener at the Castro’s Blackbird bar. But behind the scenes, his supporters were not happy.

Wiener carried the day over opponent Jane Kim, but only by slightly more than a percentage point. Wiener’s backers had been hoping for something in double digits, a result that would have discouraged Kim supporters and donors ahead of the November general election.

Instead, it’s a real horse race. What happened to Wiener’s lead in the polls?

“The city,” one insider sighed, “is in a mood.”

That’s probably true. But what’s the mood? And, more important, what does it mean in the larger picture?

Good luck in reading the tea leaves, because every time we seem to have a watershed moment, like Kim’s unexpected success, there’s someone who will say, “and yet ...”

Kim definitely had the splashier campaign. Many felt that getting the endorsement of iconoclastic presidential candidate Bernie Sanders gave Kim a “Bernie bump.”

And yet ... despite predictions that Sanders would give Democratic opponent Hillary Clinton a serious run in California — and some prognostications that he might win the state — he lost by double digits.

What’s more, in progressive San Francisco, where you’d think an avowed socialist candidate would be a rock star, Sanders was defeated by nearly 18,000 votes. How can there be a Bernie bump if even Bernie doesn’t reap its benefits?

Turnout was high

Some expectations held up. It was a high-turnout election. Almost 40 percent of eligible voters in San Francisco cast a vote, and that number will rise as late votes are counted. And, despite predictions that the inevitability of Clinton’s nomination would hold down voting, 89,220 San Francisco voters went to their polling place Tuesday.

Compare that with the June 2014 primary when just 30 percent of voters cast a ballot, with only 39,404 percent bothering to vote on election day.

So that must herald an era of voter engagement, right?

Not quite. The second-largest voting bloc in San Francisco — 30 percent — is made up of those who decline to state a political party preference. Conventional wisdom has it that the decline-to-state surge is driven by Millennials, who were supposed to be a big factor in the primary.

But for this primary they were more like “decline to vote.” According to San Francisco’s Elections Department, fewer than 30 percent cast a ballot. Hard to make the case that they influenced the race.

Same old gang

As for San Francisco’s obscure but influential Democratic County Central Committee — prepare for shouts of an epic political revolution as a progressive slate won 14 of 24 seats up for grabs.

But look at the names — Kim, John Burton, Aaron Peskin,Bevan Dufty. With few exceptions, the DCCC election is the same old gang.

If you’d like to point to a fresh face in the DCCC, try newly elected Keith Baraka, a gay, African American firefighter. You can’t get much more San Francisco than that.

The bottom line is, for all the shouting and sleazy mailers, the DCCC ended up pretty evenly split between moderates and progressives. Not much of a revolution.

Political barometer

All of which leads back to Wiener and Kim. Many have billed their race as a gauge of the ethos of San Francisco. There have been predictions that the city is becoming more moderate and that Wiener, who emphasizes quality-of-life issues, transportation and creating housing, would benefit.

Now, Kim insists that her strong showing proves that progressives “represent the majority of San Franciscans.”

I’d say it’s less ideological than that.

Wiener is actually kind of the person you’d like to have representing you in Sacramento. He’s earnest, has a legendary work ethic and churns out legislation with machine-like regularity.

Kim has her own political body of work, but with the guidance of consultant Eric Jaye, she’s been adept at creating hey-look-at-this moments. One minute she’s appearing in a video ad doing martial arts and the next she’s making an appearance with Sanders. She’s the flashier, hipper candidate, and that’s helping her.

Which means the next few months are going to be a slog for both candidates. Wiener will have to find a way to jazz up his campaign, and Kim will have to keep finding attention-grabbing issues. In addition, the stage is set for some ugly attack ads.

Chiu cruised

However, this will pass. Also at Wiener’s party was David Chiu. Two years ago he was locked in a bitter race for the Assembly with David Campos. The two battled for months, with Chiu finally prevailing by just over two percentage points.

But Tuesday night he was running virtually unopposed, racking up nearly 87 percent of the vote.

I don’t know what the city’s mood is, but Chiu’s was excellent.

C.W. Nevius is a San Francisco Chronicle columnist. His columns appear Tuesday, Thursday and Saturday. Email: cwnevius@sfchronicle.com. Twitter: cwnevius