across all criteria relevant to be elected for Partnership at BCG (and any comparable consultancy), such as problem-solving, IP develpment, people leadership, coaching, client leadership, commercial targets, etc.), the absolute threshold is not that high.
The true difficulty comes from staying above the bar in all of them and be truly distinctive in one or two and still be able to sustain the lifestyle.
Can you do the problem solving and manage a team and build relationships with clients and perform internal Firm duties (eg, lead and develop a Practice) and see your family and get enough sleep and…?
Building up the skills from Analyst to Partner is not a completely overwhelming task — because you can get guidance and support and encouragements, etc. The real difficulty comes from the cost of doing it. Drafting and tracking a work-plan is not rocket-science — but if it does not come naturally, you’ll still have to do it for 3–4 years non-stop. If you get grumpy and inefficient when you sleep less than 8 hours a night, be prepared to work on that — quickly!
For example, a Junior Partner ("Principal") may have a good track record / reputation for managing the lifestyle of the teams. However, looking behind the curtain might very likely reveal that, since he always has 3 or 4 teams working at the same time for multiple clients spread across two continents, he has to work just about every weekend for 2–4 hours, reviewing packs, on conf-calls, etc.
So at the core, it is really about the fit of this profession with your own strengths and whether you really want to make the effort to sustain that kind of life.