Bernie Sanders should leave the Democratic Party, and become the Green Party's nominee for president. The Democratic Party's establishment has never liked Sanders, because they always wanted Clinton to be the party's nominee. Sanders has gained massive support among young voters, and would likely carry much of this support to the Green Party. In short, Bernie Sanders would likely enjoy more success as leader of the Green Party.
Yes, Bernie Sanders should exit the Democratic party in favor of leading the Green party in the November election. This is because Hillary Clinton and Donald Trump have the top two spots, democratic and republican respectively, and are not looking to give it up any time soon. Bernie Sanders will have a better fighting chance if he were to switch to leading the Green party.
Bernie Sanders should seriously consider the option to lead the Green Party in the November election, since it is highly improbable that Hillary Clinton would choose him to be her Vice President anyways. It's either that or return to the Senate and give up his ambitions to reach the Oval Office. I mean, Donald Trump constantly threatens to leave the Republican Party and run as an independent, so it's questionable as to whether this kind of political flip-flopping would even hurt Sanders' career.
No, Bernie Sanders should not lead the Green party for the November election. While it is my belief that he is the most qualified candidate, joining the Green party could split the Democratic vote. With Trump as the option for the Republican party, a split in the Democratic vote could guarantee a Republican win. With the amount of hatred that Trump promotes, his win as president would certainly bring the country back to its racist past and put an end to the freedoms that Americans enjoy. Although Bernie Sanders will probably not make the Democratic nomination, a Democratic win is far more important at this point than a Sanders win.