Opinion writer

(AP Photo/Craig Ruttle)

Is the window closing on Bernie Sanders’s moment? A number of folks, your humble blogger included, have suggested as much. We’ve argued that with Democrats seeming to unite behind Hillary Clinton, it’s possible that the longer Sanders withholds his endorsement for her in the quest to make the party platform more progressive, the less leverage he’ll end up having.

But a new battleground state poll from Dem pollster Stan Greenberg’s Democracy Corps suggests Sanders’ endorsement could, in fact, still have a real impact, meaning he may still have some genuine leverage to try to win more concessions designed to continue pushing the party’s agenda in a more progressive direction.

The poll has good news for Hillary Clinton: It finds that among likely voters in nine key battleground states, Clinton leads Donald Trump by eight points, 49-41.

There are a lot of interesting findings here. One is that Trump’s Rust Belt strategy may be failing: In the aggregate of five of the states — Ohio, Pennsylvania, Michigan, Wisconsin, and New Hampshire — Clinton leads by eight, 44-36. A second is that Clinton may be able to expand the map because she’s also doing well in the more diverse remaining states: In the aggregate of North Carolina, Arizona, Nevada, and Florida, Clinton also leads by eight, 47-39.

What about Sanders’s impact? It’s true that the poll also shows that Democrats are very united behind Clinton, with 89 percent of them in these nine states supporting her.

But peek below the toplines, and it’s clear there’s plenty of room for a Sanders endorsement to help Clinton.  This becomes clear when you look at the breakdown of numbers among not just Clinton and Trump, but also with libertarian Gary Johnson factored in, because apparently, a lot of Sanders supporters are now going for Johnson.

The poll finds that among voters who supported Sanders in the primary in the nine battlegrounds polled, 69 percent support Clinton, while six percent back Trump and another 17 percent support Johnson. What’s more, among millennials, it’s even more stark: 46 percent support Clinton, 24 percent back Trump, and 22 percent support Johnson.

How is it possible that Clinton can win 89 percent of Democrats, but much smaller percentages of Sanders supporters and millennials? Greenberg tells me that one possibility is that many of them are identifying in the poll as independents, which means that, if Clinton can win them over, her lead over Trump could actually grow larger.

“It’s quite possible that many Sanders voters and millennials may be identifying as independents,” Greenberg says. “Millennials, and white millennials in particular, are still out there and have not consolidated behind her.”

“Of his vote, there’s still a significant bloc voting for the Libertarian Party,” Greenberg continues. “Ninety percent of Sanders voters should be voting for Hillary.” If Sanders were to succeed in consolidating his voters and millennials behind Clinton, Greenberg adds, “it could kick her lead into double digits.”

This dynamic is also borne out in this week’s Washington Post/ABC News poll, which found Clinton up by 51-39 among registered voters nationally. According to figures provided by the Post polling team, among people who wanted Sanders to win the primary, Clinton leads Trump by 65-9, which is substantially less than she should be winning. That’s because an additional 19 percent of them now say they’ll back either libertarian Johnson or Green Party candidate Jill Stein.

A Sanders endorsement of Clinton, presumably, could change this. But Sanders continues to withhold his endorsement, for the explicit purpose of winning more concessions in the party platform when the full Platform Committee meets in coming days, and he has even signaled that he may still hold out until the Democratic convention begins in Philadelphia in late July.

The mood in the Clinton camp about this, as best as I can determine, is that Clinton and her top advisers very much want Sanders’s endorsement and are in serious talks with him about what sort of platform concessions — and what sort of role for Sanders — will be necessary to get it. But there is no sense of alarm among Clinton’s team that I can see. Elizabeth Warren is filling up the space that Sanders might have filled, making an aggressive case for Clinton’s candidacy — and against Trump — to Democrats and progressives nationally. The process of Dem consolidation is under way, even without Sanders’s explicit advocacy on her behalf.

That said, it is clear that Sanders’s endorsement could expand Clinton’s lead over Trump in a non-trivial way.  In a race that could end up getting a lot closer, the Clinton team obviously wants the additional room for error that winning most of Sanders’s supporters might provide. And if it doesn’t get closer, winning them could conceivably help lay the groundwork for a much larger victory in November, potentially making governing easier.