Even before the impeachment inquiry against President Trump was announced on Tuesday, the president’s re-election campaign blasted an email to supporters, urging them to defend Mr. Trump against the “baseless and disgusting attacks.” Facebook quickly filled with ads for impeachment-themed merchandise, including $3 “Impeach Now!” bumper stickers and $35 “Impeach This!” T-shirts. In a private chat room, pro-Trump internet trolls discussed which memes, videos and news stories to push on social media in order to reclaim the narrative.

The last time America watched an impeachment inquiry, it was largely an analog affair. When the House voted to begin impeachment proceedings against Bill Clinton in 1998, only one in four American homes had internet access. AOL and Yahoo were the biggest websites in the world, and “tweet” was a sound birds made.

If the inquiry opened by House Democrats this week results in a formal impeachment of Mr. Trump, it will be the first of the social media era. In many ways, it is a made-for-the-internet event. The political stakes are high, the dramatic story unspools tidbit by tidbit and the stark us-versus-them dynamics provide plenty of fodder for emotionally charged social media brawls.