I've worked on plenty of collaborative projects, and they typically end well. We share the work, we talk over what to present to our manager, we share findings.
Recently I've been assigned to a project with someone new. He is eager and enthusiastic. We worked several hours on a thorough outline for the project, which we were to present to our manager the next day.
The hour of the meeting, I go in, and it turns out Coworker has changed almost everything on the slides. He also loudly goes over the presentation, not allowing me the chance to cut in or explain (if it matters, I am more soft-spoken in comparison, but have given plenty of successful presentations in the past).
Coworker also goes over all the "research" he's done prior to the meeting, none of which he has shared with me. He makes bold proclamations, like "I found a way to track the data," or "I put together the notes for..." In past group projects, it was a mutual understanding that group members always used "we" instead of "I" as a collaborative effort. When the manager asks if we have additional questions, Coworker cuts in confidently with "Nope!" and a charismatic smile, so I feel hesitant to speak up.
But the kicker is, when I ask Coworker afterward about all the "research" he did, such as where to find data sources, he says he doesn't know, but read a sentence about it somewhere in an obscure source.
So now our impressed manager thinks we have everything we need to proceed, even though we are still at step 0 in terms of data sources and everything. Is it professional to bring this up with my manager? I would essentially be throwing my Coworker under the bus, but he has also thrown me under by taking the reins of this project behind my back.