Hillary Clinton is the Democratic nominee, full stop.

No, she didn't formally clinch, and Bernie Sanders picked up victories in Colorado, Minnesota, Oklahoma and Vermont. But the overall numbers are clear. Clinton crushed Sanders in the states she figured to win, and has kept it close in most states she figured to lose. For example, FiveThirtyEight estimated she needed to win Virginia by 9 percentage points but she was winning by almost 30. In Georgia, she needed to win by 27 points, but she was ahead by more than 40; and in Massachusetts, Sanders needed to win by 11 but she won it narrowly. 

Large leads are difficult to overtake in the Democratic presidential race because strict proportional allocation of delegates means that even a slumping front-runner continues to get closer to locking up a majority. Nothing in the election returns to date, or polls of future states, or anything else indicates any nomination trouble ahead for Clinton. 

A lot of people underrate her as a politician. I suspect it's because she isn't good at delivering speeches. I can't think of a major-party nominee in the video era (say, from 1952 on) who was significantly worse than she is at it, and most have been better, some by a lot. Her effort on Tuesday night was as pedestrian as usual. 

But public performance is only one part of what politicians do, and speeches are only a part of that. She's good at other parts of public performance, including debates, one-on-one interviews and grillings by hostile congressional committees.