The only time Biden wasn’t in the drivers seat was after the Nevada caucus when Bernie Sanders was the front runner
And even then, it wasn't really a case of "Biden was no longer in the driver's seat" so much as it was one of "somebody else finally wrestled the steering wheel away from him for once, if only for a second or 2." Remember, the NV debate was the real start of Biden's comeback: he finally did well at a primary debate for once, everybody was mostly distracted by Warren's castration of Bloomberg anyway, & then he was able to parlay it into coming in (an admittedly distant) 2nd in NV, which is what led to the Clyburn endorsement, which is what led to the SC blowout, which led to the Super Tuesday massacre, etc., & the rest is history. At best, the only point in time at which he'd truly lost the position of sole frontrunner was after his utter collapse in IA & NH, at which point their maxim became "start trying for once because in the name of all that is holy, we just need to make it to SC." And it worked.
Biden also won that South Carolina debate
