On the Democratic side, the race between Hillary Clinton and Bernie Sanders is mostly over. Sanders will be able to fund his campaign until the Democratic National Convention, but he won't have the delegates to win. And, by and large, that isn't a terribly surprising result. One thing we've learned since 2004 is that the liberal wing of the Democratic Party has money, and will fund candidates they like. In 2004, that was Howard Dean. In 2008, that was Barack Obama and John Edwards (before it was revealed he was a slimeball). So, its no surprise that Bernie Sanders is pulling in gobs and gobs of money.
But, and this is the key point, the liberal wing of the Democratic Party is not as big as it thinks it is. Because of the perceived/real racism of the Republican Party, most minority voters - African Americans, Latino/Hispanic Americans, and Asian Americans - vote Democrat. Now, as anyone who's been around these voters can tell you, not all of them are liberal. In fact, many African Americans and Latinos are fairly conservative. George W. Bush and Karl Rove recognized this, and tried to woo them over to the GOP, only to be undermined by the large number of racists in the Party. That leaves a fair number of minority voters in a pickle - vote for the candidate who's views are more liberal than their own, or vote for the candidate who seems a bit too comfortable with racists. Add to that the fact that Republicans are actively seeking to prevent minority voters from voting, and the fact that a fair number of minority-majority districts aren't all that competitive, and you get crappy voter turnout. What made Obama so initially successful was his ability to mobilize the liberal wing of the Democratic Party, and also mobilize minority voters.
But outside of Obama, minority voters represent the Democratic Party's "Peoria Test." If you think back to the old days of Hollywood, studio execs would ask, "but will it play in Peoria" as a way to determine if a movie would be successful or not. Since minority voters aren't necessarily liberal (though many are), being able to play to those voters is key.
The one thing that we've seen over the past several primaries and caucuses is that Bernie Sanders isn't playing well in Peoria. He has a strong pull with the Party's liberal wing, but outside of that, he just isn't getting the kind of traction with minority voters to beat Clinton. Keep in mind that when Obama ran in 2008, he generated record turnout. Sanders just isn't cutting it.
And from my perspective, that's not terribly surprising since Sanders has never been a star on the national stage. He's been in Congress for over 25 years, and outside of him being a Socialist, and being from Vermont, there hasn't been much to say about him.
But with that said, Sanders has managed to do one thing very well - he's pulled Hillary Clinton to the left. For the past thirty years, the Clintons have been moderates and have pulled the Party to the right. By and large, they've done that because that's where the votes are (more on that below). In fact, when the Clintons tried to go with a big government plan, they were annihilated - Hillary especially. And much of their other conservative legislation - DOMA, Don't Ask/Don't Tell, the Crime Bill - was largely created to head off a much worse conservative bill. And this legislation existed in an era of swing voters. Those days are over, and now both Parties know that to turnout is key to winning elections. Moving to the left helps Clinton, and Sanders is pushing her leftward every day.
Lastly, for those of you who are upset that the Democratic Party can't put forward any better candidates, I have a quick word for you - if you don't vote, candidates who share your preferences don't get elected. Liberals and moderates got killed in the elections of 2010 and 2014 because people didn't turn out to vote. So, we're stuck with a Congress that refuses to do anything. That's on us.