Donald Trump’s lengthy Twitter history has long been mined by his opponents, looking for ghosts to haunt the president with accusations of hypocrisy. He was critical of military intervention in Syria under President Barack Obama; so when as president he launched missiles at a Syrian base, those old tweets of his slamming Obama were retweeted back into relevance.

On Thursday afternoon, Trump used this trick on someone else: He retweeted an old tweet from Rosie O’Donnell demanding that FBI Director James Comey be fired, and commented, “We finally agree on something Rosie.”

And O’Donnell responded:

For context, the Trump-O’Donnell feud has lasted more than a decade. It began when the comedian insulted Trump on “The View” in 2006; Trump responded by threatening to sue her, or, as he put it, “taking lots of money from my nice fat little Rosie.” In fact, the first three times that Trump ever tweeted about a “loser,” he was talking about O’Donnell. He also repeatedly mentioned O’Donnell during the presidential debates. When Megyn Kelly asked him in 2015 to answer for past remarks that referred to women as “fat pigs,” “dogs,” “slobs” and “disgusting animals,” Trump’s reply was “Only Rosie O’Donnell.”

So it’s not too surprising that if this particular president of the United States were to take time out of his day running the country to mock a celebrity, that it would be her.

O’Donnell also tweeted the following at Trump earlier this week:

But how did Trump see O’Donnell’s old tweet about Comey that he eventually retweeted?

The first possibility is that Trump or someone on his staff saw it via r/The_Donald, the popular subreddit dedicated to supporting him. A Redditor posted it there a few minutes before Trump’s tweet, with more vicious commentary.

Trump has tweeted things before that were popularized on r/The_Donald, like this old photo of Sen. Charles E. Schumer (D-N.Y.) and Russian President Vladimir Putin.

That photo appeared on the Twitter feed of Dan Scavino, Trump’s director of social media, shortly before the president’s own tweet. Politico previously reported that the Trump campaign actively monitored pro-Trump social media, including r/The_Donald, and coordinated to some extent with the board’s more active members. Potentially viral posts were sent to Scavino, Politico reported — although spokeswoman Hope Hicks downplayed the extent to which the campaign monitored social media. In any case, there’s plenty of public evidence to suggest that those close to Trump monitor and participate in the Trump-supporting parts of the Internet, and r/The_Donald is certainly one of the most influential of them.

But r/The_Donald wasn’t the first to pull up Rosie’s old tweet, and it didn’t really go viral there until after Trump tweeted it out. The post had just a few upvotes and comments at the time of Trump’s tweet, meaning it likely wasn’t very visible on the subreddit’s main front page (it would be visible if someone were monitoring the subreddit’s list of “new” posts, however).

So there’s another possibility: that Trump, or someone on his staff, saw the tweet of Trump-supporting radio host Ann Vandersteel, who posted the same image a day ago and got thousands of retweets.

And a couple of people also tweeted the old tweet and tagged @realdonaldtrump last night:

Anyway, thank you for reading this important investigation into how the president of the United States might have found and retweeted an old tweet by a comedian with whom he has a longstanding feud.

The White House on May 11 continued to defend President Trump's dismissal of James B. Comey as FBI director. (Bastien Inzaurralde,Alice Li,Jayne Orenstein/The Washington Post)

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