In mid-March, then-FBI Director James Comey testified before the House Intelligence Committee about the bureau’s investigation into the Trump campaign’s connection with Russia. The testimony received a massive amount of coverage — significantly more than any other development in the saga to that point.

And it was deserved: Top US officials were investigating whether a foreign government had improper influence on the sitting president of the United States and/or his associates.

But the buzz died down, and for weeks the Trump-Russia investigation was barely mentioned on US television.

Even when Comey testified last week in front of the Senate Judiciary Committee — saying it made him “mildly nauseous” that he might’ve affected the election — the news coverage didn’t match that of his House testimony. It seemed that story would die down as well.

But on Tuesday, Trump fired Comey, who was in charge of investigating his administration. Members of both parties criticized the move. It drew comparisons to the Watergate scandal. It was a story that probably would have withered away — but by firing Comey, Trump turned this Russia story into a two-headed monster that is growing further out of his reach.

Comey’s testimony in front of the House Intelligence Committee, which had a lot of staying power, went away after a week or two. In fact, there were days after the testimony when fewer than two people on national TV uttered the words “Trump,” “Russia,” and “investigation” in proximity to each other.

To create the chart, Vox used iQ Media to sift through transcripts of cable news and find instances when those terms appeared within 20 words of each other. As you can see from the chart, the news of Comey’s firing outpaced any of the previous news.

It’s not just about the size of the spike. After all, the dossier alleging that Russia had embarrassing intelligence on Trump created even more buzz — and that faded quickly. (That isn’t on the chart because it wasn’t related to an investigation.)

Rather, Trump should worry that his firing of Comey created a substantively different storyline. As my colleague Matt Yglesias writes:

Nothing we’ve seen credibly reported thus far about Trump and Russia would amount to an impeachable offense, and indeed, it’s not really clear what allegations of “collusion” on the campaign trail would really amount to even if proven. Firing the FBI director in order to obstruct an ongoing investigation would be different.

Trump made this Russia story more powerful — but unlike the previous storylines, this new wrinkle might have enough endurance to outlast him.