Here’s what Sanders said last week: “The major political task that we face in the next five months is to make certain that Donald Trump is defeated and defeated badly. And I personally intend to begin my role in that process in a very short period of time.”

Just not yet, apparently.

Days after primary defeats in California and New Jersey, Sanders started laying off at least half of his campaign staff while calling himself an “active candidate” and pledging to “take our campaign for transforming the Democratic Party into the convention.”

His decision to not concede the nomination makes some sense if you think about the full arc of Sanders’ campaign—which no one ever really expected to seriously contest the nomination but instead to have an impact in making the party and its eventual nominee more progressive. Still, as the primary slogged on, and Sanders became an actual electoral threat, the campaign became a real fight.

In the beginning of January, Clinton posted favorability ratings among Democrats in Gallup polling at 58% to 61% versus Sanders hovering consistently 10 points lower. By April, their positions had switched, and Sanders had about a 16 point favorability spread over Clinton with Democrats—with Clinton dropping to 43% favorability and, as of June, just 39%. In other words, it’s reasonable to argue that the campaign between Sanders and Clinton made Clinton less popular among the Democratic base—maybe because voters simply had an alternative to prefer or because Sanders actively undermined perceptions of Clinton. Either way, the damage was done and now needs to be repaired to help Clinton win in November. And among a certain swath of often vehemently anti-Clinton progressives, Sanders is perhaps the only one who can lead that healing.

Instead, Sanders has chosen to send mixed messages about his candidacy which, the longer he waits, in effect sends increasingly mixed messages about Clinton. Clinton will be the Democratic nominee for President of the United States. And the longer Sanders waits to endorse her, the more reluctant and thus tepid that endorsement will seem. Plus, it only creates space for his most ardently anti-Clinton supporters to fume and foment.

There’s been speculation that some of Sanders delegates could try to deny Clinton the nomination during the Democratic National Convention. That would flaunt the democratic process and damage the party at the moment it most needs to unify. But every moment that Sanders’ refuses to formally concede gives comfort to such plots. It’s time for Sanders to emphatically and enthusiastically support Clinton’s candidacy and send a clear message that anyone who tries to attack or undermine Clinton’s candidacy will be going against Sanders and the spirit of his campaign.

I believe in the mission and message of Sanders and his candidacy. I firmly believe we need a revolution in the Democratic Party and nationwide that finally makes America work for the 99% and not just the establishment elite. I want to see the energy and excitement behind his vision carry forward, animated by a bold new movement of engaged progressives willing to challenge the Democratic Party and the political system—raising up a truly transformative agenda and holding all of our leaders accountable.

We can do that AND support Hillary Clinton—emphasizing the 90% of issues with which progressives agree with Clinton while continuing to push her to evolve on the rest and taking her to task when she doesn’t. I’m not saying this is an easy needle to thread, arguably the left failed to do this for the first four years of Obama’s presidency. But this is the task ahead, the way to raise up our vision and defeat the greatest threat to that vision, Donald Trump. We progressives can thread that needle with the right leadership. These are the moves Sanders should be making—instead of playing limbo.

This article was originally published on Time.com.