A statement made inside your own mind and heard by no one. That's effective.
Of course not, but you're entitled to your right to vote in all of the various elections that have a substantial impact on your day to day life (state and local matters far more than federal on this front) and while you're at it I'd argue that Trump's platform is entitled to a pretty strong "NOPE" vote, a response that is only heard if it is cast for the opposing party anyone actually pays attention to.
The presumption in political circles is that you could put up anyone with an (R) and a (D) after their names and between them they'll each get about 45% of the vote at a minimum. The remaining 10% is the flux that decides who wins. Voting Clinton and landsliding Trump is a step towards shattering that dellusion, a delusion at the very heart of why politicians feel it is in their best interest to work for rich donors over their actual constituency.
A strong non-partisan repudiation of Trump is the single best thing any of us can do in the general election to push against the establishment politics status quo.
If you've been playing the game for 20+ years I'd think you would have some recollection of candidates who proceeded Sanders. He isn't some magical snowflake.
Barack Obama was a step to the left for the DNC at the time he won the nomination and his appeal is largely what let candidates like Elizabeth Warren get mainstream party acceptance. Howard Dean was a serious candidate in 2004 and ran well to the left of the establishment. He ended up as the DNC chairman not long after and got to effect some legitimate change in the party platform. Bill Bradley ran on almost the exact same platform as Sanders in 2000 against Gore, though obviously with little success. Gary Hart was a reform candidate and had a lot of momentum in '88 until his personal drama brought him down.
At the same time there was a strong, united GOP throughout the 80's to contend with so the Dems were playing to the middle in an attempt to stop losing elections, that's just the nature of politics. When the right keeps winning everyone is forced to move right. Just like how if Clinton wins we'll see everyone forced to move left following a second left leaning POTUS.
If you go back before the Reagan era you had McGovern, every bit as left as Sanders and 40 years sooner, as the party's nominee in '72. Carter ran against a host of far more liberal candidates in '76 but beat them because the primary system had finally taken more importance then the party bosses and Carter used that to rack up delegates while the more liberal candidates languished.
The reality is that the next Democratic Primary will likely see a broad swath of candidates, every single one to the left of Clinton, and without the gravitas that Clinton has it will be something of a free for all.
What candidate isn't? Obama is the "best" candidate we've had in generations and he is frequently derided for being too pragmatic and a centrist when serving in an office that literally demands a pragmatic centrist.
That all depends on how down ballot elections, the mid-terms, etc. turn out. Your vote gains more and more power the further down the ballot you get (as it gets more local) and that is where metrics are really shifted. The GOP hasn't made this insane leap to the right out of nowhere. They've done it at the behest of the Tea Party, who have been taking over local offices and State Houses across the country. Rock the vote locally and the national ticket will follow.
Also, I'm betting come 2024 we'll see a currently completely unknown candidate step forward with a strident, charismatic message that will dominate the Democratic Primary from an ideological standpoint, sweeping the party up into an Obama-like fervor. The real question is where the nation stands at that point and if such a candidate can translate that momentum into moderate appeal.
