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, the political website FiveThirtyEight estimated she needed to win Virginia by 9 percentage points; 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.