Vanguard knows how to come from behind, but now its rampant success in the investment world is testing whether the Malvern-based company knows how to lead.

Vanguard has been No. 1 in mutual funds since it surpassed Fidelity Investments in 2010, and its lead continues to widen with asset growth of $1 billion per day, according to a Fortune feature by Erika Fry.

Refocused on a broader portfolio of goals after 2009 workshops with business expert Jim Collins, Vanguard today is sailing full speed ahead with $3.8 trillion in assets, the industry’s largest sum of money in target-date retirement funds, the second-highest amount in ETFs, and rapid expansion in financial advising and international accounts.

But shifting gears so quickly has led to growing pains. The hiring growth, in particular, “strains the organization,” CEO Bill McNabb said.

And more importantly, Vanguard has been confronted with the prospect of increasing its leadership in the arena of advocacy.

“That is one of the biggest byproducts of our success that needed to be addressed,” he said. “We think of this as an incredible responsibility to get it right.”

And just because Vanguard has built its empire on more “hands-off” indexing doesn’t mean it won’t stand up for investors.

“People think that because we have a lot of indexed assets, we’ll be a passive owner,” McNabb said. “We don’t think that’s true. We want long-term results, not short-term.”

Read more of Vanguard’s history and current challenges in Fortune here, and check out previous VISTA Today coverage here.