In this 2005 frame from the now-infamous video, Donald Trump prepares for an appearance on “Days of Our Lives” with actress Arianne Zucker. He is accompanied by “Access Hollywood” host Billy Bush. (Obtained by The Washington Post/ )

Although it seems like an eternity, it’s been less than a week since a video from 2005 featuring Donald Trump rocked the political world.

Now, the candidate’s boast about his ability to sexually assault women has opened a floodgate for credible allegations. Trump’s presidential ambitions may well be dead in the water.

What if that campaign-changing video — or something equally incriminating — had emerged during the Republican presidential primary, instead of sitting on a shelf at NBC’s “Access Hollywood”?

And why did it take NBC News so long to break a story that took The Washington Post only five hours, from initial tip to publication?

Mark Kornblau, a spokesman for NBC News’s chairman, Andrew Lack, gave me some answers in a phone interview but left some mysteries unanswered.

When did NBC News learn about the video?

Not until Monday of last week, Kornblau said, when Noah Oppenheim, executive producer of the “Today” show, first learned of it.

Kornblau denied reports that anyone in the news division knew about it last month when Billy Bush, who appears in the video with Trump, talked about it while covering the Olympics. (Bush, a former co-host of “Access Hollywood” and current “Today” co-anchor, is currently in negotiations with the network on a separation agreement.)

By Tuesday of last week, Lack had read a transcript. “The immediate judgment was that it was of high news value,” Kornblau said.

“Tuesday was when the clock started,” and after that, the focus was on “how to do all the journalism and reporting, and asking what legal boxes needed to be checked.”

Lawyers worked it over for a few days, and gave a go-ahead Thursday, Kornblau said.

If NBC lawyers gave the all-clear Thursday, why did The Post’s David Fahrenthold, rather than NBC, break the story Friday afternoon?

Kornblau said that NBC News had agreed to let its entertainment-side cousin, “Access Hollywood,” break its version of the story first — “as a courtesy” — because it was the source of the recording.

That “probably, but not definitely” would have happened Friday night. If it hadn’t, it’s likely that the news division would have aired its story first, he said.

Is NBC News right now scouring “Access Hollywood” recordings to see what else Trump said, given the hundreds of interviews he did on that entertainment magazine over 20 years?

(Another cache of recordings, those surrounding the NBC reality show “The Apprentice,” are owned by MGM now and aren’t available to the network’s news staff.)

Kornblau said that NBC journalists are researching everything available to them, but he said the “Access Hollywood” recordings “are not our archive.” He declined to answer my question about whether that search is being done, even now, by NBC journalists.

An “Access Hollywood” statement last weekend that they have now been through their archives and not found anything of great significance doesn’t reassure me for a second. “Access Hollywood” is part of the entertainment division of NBC, not news.

Would Billy Bush’s portion of the video have been edited out, as some have suggested?

Kornblau scoffed at the notion: “It would have been insane to do that.” And, he added, it wouldn’t even have been possible from a practical point of view, because the Trump/Bush conversation was so intertwined.

Why wasn’t it broadcast Friday morning at the latest, especially given the presidential debate scheduled for Sunday night?

Kornblau said that Lack was not trying to beat the clock to get it broadcast before the debate Sunday.

That “was not part of the thinking,” he said. “The way Andy looks at it is, when you’re ready to report, you report it.”

As it turned out, however, having the revelations out before the debate made a huge difference. Moderator Anderson Cooper pressed Trump repeatedly about whether he had ever actually done what he was bragging about — groping women without their consent — and Trump said no. He said it was just locker-room banter.

Now, women have come out in droves, and, if even some of them are telling the truth, Trump was lying.

Why hadn’t NBC done a rigorous search of its own archives months ago?

Kornblau drew the distinction between news and entertainment sides of the corporation, saying that the news division had indeed scoured its own archives, for example, from “Meet the Press,” turning up stories along the way.

But he said, what “Access Hollywood” has in its files “is not NBC News’s archive.” But it certainly was newsworthy.

The entertainment-news split at NBC seems to have caused plenty of trouble already.

If a corporate barrier between news and entertainment is keeping NBC’s journalists from digging in to newsworthy material, it shouldn’t be there.

In fact, it should have been torn down months ago.

For more by Margaret Sullivan visit wapo.st/sullivan