OK, for the moment, let's ignore the fact that the popular vote metric is one that Clinton floated a few weeks ago because she was losing everywhere else. Let's ignore the fact that it under represents caucus states. Let's just look at this US News and World Report column that states that Clinton will take the lead in popular vote by the end of the election.
The column purports to be a case for Clinton, but it really shows how daunting the task is for her. Look at the projections.
He gives 20% victories to Clinton in PA, IN, MT, and SD... and those are the states (outside of 10% Obama victories in OR and NC in a brief concession to reality) that he considers close. Puerto Rico is a wild card and Kentucky doesn't have great demographics for Obama, but 65-35 victories seem a tad on the high side. As for West Virgina, Barone doesn't just think that the one poll there is accurate, he projects that Clinton will double her gap there. He's calling for a 70-30% Clinton victory.
People are already trying to push this column as a reasonable projection and a reason for Clinton to stay in the race. Not everyone is going to read all of the way down to the bottom of the column to get to his projections. If you see this article promoted as fact, my suggestion is to do what I do.
I have an open bet on MyDD for these odds. If anyone wants to bet me that Clinton will take IN and give me 20 points or give me 40 points in WV, I'm willing to take it. For some reason, the people pushing the column as being realistic have ignored my request even though I'm both giving them better odds to win (I said I'd have to win both IN and WV, they'd only have to win once) and offering bigger payouts for them.
I'll grant the point of the column. If Clinton lives up to those projections, she would, in fact, have a great argument to be the nominee. However, they might just be slightly unrealistic.