In the span of a week, Joe Biden usurped Bernie Sanders as the 2020 Democratic frontrunner, but also as the candidate getting the most online attention, according to data from NewsWhip exclusively provided to Axios.

The big picture: The 41 million interactions (likes, comments, shares) on Biden stories on social media last week is by far the highest level of attention any one candidate has received in the primary in a week, a reflection how much the race now centers around Biden.

Flashback: Just last week, Sanders was attracting more attention than the rest of what was then a five-person Democratic field combined. Sanders had 27.4m interactions, while Biden had just 9.4m.

For all of February, just as he held the advantage in polling, Sanders had more interactions. During the week of Feb. 16, he had 29.2m compared to Biden's 3.3m.

The big picture: In a reversal from the early stages of the race — when media cycles and engagement levels drove polling changes — it's now the election results that drive media coverage and interaction levels.

Between the lines: Top-performing stories about Biden included mainstream outlets reporting on fellow moderates dropping out of the race and endorsing him, as well as right-wing sites pouncing on his verbal gaffes and bouts of forgetfulness.

Sentiment around Sanders remained positive, with top stories including an analysis showing Medicare for All would increase wages and jobs and Sanders decrying the presence of a Nazi flag at a rally.

Our 2020 Attention Tracker is based on data from NewsWhip exclusively provided to Axios as part of a project that will regularly update throughout the 2020 campaign.

Go deeper: See all past editions of the tracker