Simply put: I lack faith in a wide swath of the American Left. I have been to "the revolution" repeatedly over the past two decades, and it isn't coming.
What happened to Ralph Nader and his movement after 2000? Where was the coordinated effort? What happened to Howard Dean's supporters after 2004? Dean himself started the Democracy for America PAC and became chair of the Democratic National Committee (DNC), and led the effort to take back the House and Senate – but it didn't happen because of the Left Flank. It happened because Dean loosened the party candidate recruiting requirements around abortion and gun control.
What about all those Ned Lamont supporters in 2006 in Connecticut (and across the country) who were so excited about beating Joe Lieberman in the primary only to lose to Joe Lieberman in the general? The Left had a huge win in 2008 with election of Barack Obama… and then we handed back the House in 2010 in a huge wave with miserable turnout for Democrats. We held the line in 2012 and then gave up the Senate when the Left failed to show up in 2014.
This is a democratic country and it is absurd to blame Barack Obama for somehow failing to inspire people. Look at our fellow citizens on the Right: when they don't get what they want, they push harder. Our team pouts and goes home. Although I do prefer Secretary Clinton to Senator Sanders for some policy reasons, the single biggest reason is that she has been fighting this fight for 25 years and is still standing.
When swaths of Democratic voters fail to materialize in the 2018 midterms, Clinton will have no illusions and have full command of the tools to keep advancing on Left Wing policy objectives. She's ready to face a hostile Congress. Sanders – who I'd support full-throatedly if he secured the nomination – needs a friendly Congress to do anything that he's talking about and I see no evidence that the our voting coalition is reliable enough to hand him that Congress (and certainly not to hold onto it).
Sanders, to his credit, acknowledges this and exhorts his supporters to that end… but he is far from the first to have done so. Past behavior is the best predictor of future behavior, and the voters that liberal & progressive politicians need in order to keep making progress flake out every time. It's as if people who complain about the status quo are actually content with the status quo of complaining about the status quo.
We've done this dance; President Obama was aiming for transformative change, got some impressive things accomplished in 2009 & 2010, and then we – not he – surrendered control of Congress by losing it without a fight. Bernie may exhort to his heart's content, but we have repeatedly shown that we can only be bothered to show up once every four years. Hillary may have her flaws as a politician, but our flaws as a coalition of voters are far more serious.
(From Quora)