I joined a company a few weeks ago. I'm a team manager responsible for several projects managed my PMs.
One of them is sponsored by very senior stakeholders at my company. The stakeholders and my predecessor signed the plan, participated in the steering committee, etc.
There were several issues with the project that came up in the last weeks. All of them are now solved. The senior leadership celebrated that "we are getting forward!" and is expecting the launch by the agreed deadline.
I think that's totally improbable.
When I look at the project plan, the regularity with which the issues come up and how much it takes to solve them, I don't believe the go-live will happen on time. There's nothing super critical, but in the planning phase the PM seems to have gone for the best-case scenario. The problem is this doesn't work for most projects and we currently see that. The issues we've had show that the project is much more complex than previously expected. At the same time, the project wasn't planned very well, which means that there are no clear missed milestones or KPIs.
The project has a huge visibility so if I now raise a red flag and tell the sponsors that I don't believe the project will succeed by the date planned, this will come across badly. Also, there are no huge red flags - no missed milestones, etc., just my "gut feeling" and expertise in projects, which obviously isn't a reliable thing.
If I don't mention that, the project will probably fail at least by 2-3 months, maybe much more.
What is the most politically savvy way to approach that? I suck at politics, so any tip is welcome.