Bernie Sanders won't be the Democrats' nominee for president. He didn't explicitly concede in last night's video announcement, but the writing is on the wall.

So if the goal of Bernie's movement is no longer "make Bernie the nominee," what is it?

Sanders wields a dedicated following, a massive email and fundraising operation, and considerable clout to affect down-ballot races and the Democrats' overall goals. He reiterated essentially his entire policy platform last night. But it might behoove him to pick something concrete that his followers can organize around, push the rest of the Democratic Party on, and make some real measurable steps on in a relatively short timeframe.

A $15 national minimum wage is one obvious option. But along with that, I'd humbly suggest he bring the full force of his resources to bear on passing his $1 trillion infrastructure proposal. And he should do it immediately.

There are two reasons for the urgency. The first is that the American economy desperately needs the boost.

The official unemployment rate may be 4.7 percent. But job growth has stalled and there are signs of weakness in the overall economy. Moreover, there's good reason to believe the unemployment rate is badly failing to capture just how many Americans could be working right now and aren't.

White House economists and Standard & Poors estimate that $1 billion to $1.3 billion in infrastructure spending can generate 1,300 to 2,900 jobs, respectively. So Sanders' $1 trillion injection could give us at least 1.3 million jobs. That's a lot!

But aside from job creation, massive infrastructure spending is also a good idea on its own merits. A widely-cited 2013 report by the American Society of Civil Engineers determined that at least $1.6 trillion needs to be spent between now and 2020 to properly update the country's electrical grid, highways, seaports, airports, public transit, water systems, dams, and more. Because of increased competition, new jobs ought to boost productivity growth in the short run, but repairing and updating the physical systems that so much of our economic activity relies on would boost it over the long run.

Hillary Clinton is certainly aware of all this. But in keeping with the over-abundance of policy caution she's shown during the campaign, her own infrastructure proposal calls for $275 billion in spending, plus another $25 billion for an infrastructure bank. That second part in particular is a good idea, but Clinton's overall numbers are grossly underpowered compared to the economy's actual needs. She and the rest of the Democratic Party need to be pushed left here — and with his clout and alternative proposal at the ready, Sanders is the obvious person to do it.

Which brings us to the second big reason Sanders should do this now: the freak, once-in-a-lifetime event that is Donald Trump's ascension to the GOP nomination.

It looks increasingly likely that Trump will lose so badly he could hand the Democrats the Senate and more leverage in the House. But unless the GOP defeat is truly cataclysmic for down-ballot races, Hillary Clinton will likely have to find common ground with congressional Republicans to get anything done — and we've seen how that's turned out for President Obama.

That's where infrastructure comes in. It might be one of the rare places where compromise is actually possible. It's hard to overstate how wildly popular infrastructure investment aimed at job creation is with the broader public. And by calling for his own"trillion-dollar rebuilding plan," Trump himself has revealed that the GOP's voter base might actually be remarkably amenable to Sanders' proposal.

So Bernie has the right idea and leverage at the perfect moment. He should seize it.