Bernie Sanders is the front-runner in several Democratic primary polls for Iowa and New Hampshire, is within striking distance of first in Nevada, and has cut Joe Biden’s national lead to single digits.

That’s a sentence I could have already written a few weeks ago — but since then, a lot has changed. First, Sanders became the face of opposition to Donald Trump’s military strikes against Iran, working with Rep. Ro Khanna to introduce the No War Against Iran Act. Then, he spoke out against Trump’s plan to cut Social Security. Both of these stands against Trump are enormously popular with the Democratic base and with the broader set of voters Sanders needs to win in November.

And both of these stands have also drawn attention to Joe Biden, who voted for George W. Bush’s disastrous Iraq War, and who has repeatedly called for cuts to Social Security. Sanders, favorably positioned in the polls, is fighting two major battles against the front-runner, and he is on the right side of both of them, and this is happening just days before the Democratic primary voting begins.

That is all you need to know about the barrage of utterly implausible, thinly sourced, guilt-by-association attacks suddenly targeting the Sanders campaign. In a few hours, Bernie Sanders will take the debate stage in Iowa, where he will fight to save Social Security and Medicare and to reign in the reckless militarism of war hawks like Joe Biden. And pundits and politicians who don’t share these priorities are going to try to derail that debate into a petty gossip session on a series of thinly sourced allegations and pseudo-scandals.

Everyone knows why James O’Keefe released his latest video attacking Bernie Sanders just hours before tonight’s debate. And everyone knows why Donald Trump, teeing O’Keefe up for his announcement on Sunday, wrote that “Sanders is surging in the polls, looking very good against his opponents.” Bernie’s opponents see him poised for a major win in Iowa, and so their hope is to transform tonight’s debate into a high-profile oppo dump against him.

That’s why O’Keefe’s video is only one of three sensational stories about volunteers and low-level staff behaving badly that just so happened to break since the weekend. And that’s obviously why reporters suddenly got wind of a two-year-old conversation where Sanders, according to the Washington Post , said “that Trump would use nefarious tactics against the Democratic nominee” — an utterly banal statement that Bernie’s opponents are trying to spin as problematic.

I do not envy the task that lies before Bernie Sanders tonight. His goal will be to parry an endless barrage of attacks and pivot the conversation, again and again, back to the issues that matter: war, an economy that works for the many instead of the few, and defeating Donald Trump in November. But even if they can’t land a clean hit on him, Bernie’s opponents will try to put him on the defensive and bury him in an avalanche of suspicion. The media, meanwhile, will be eager to hype any epic zingers from his opponents — or any “cut the bullshit” clapbacks from the moderators.

But this is a fight we can’t afford to lose. And fortunately, Sanders isn’t alone in this fight: right now, armies of volunteers are knocking on doors and making calls in Iowa. This is a war that was always going to be won on the ground, not in the media; if Bernie’s still standing when this night is over, and if his supporters continue to stand with him, we have a world to win.