I get what you are saying. If enough people write in Bernie to swing the election to Trump, then they helped Trump and all his horrible policies move into the most powerful office in the world. I still maintain that it's up to Hillary to win those voters over and the choice of who to vote for is personal.
Here is what one person who voted for Nader said. I'll excerpt a couple of paragraphs and provide a link if interested in the whole thing:
This section talks about how Gore made a strategic miscalculation about the strength of opposition to him from the left:
It cannot be stressed enough that had Gore instead embraced an even slightly more progressive agenda, he would not have lost so many Democratic voters to Nader. Rather than modify his positions more in line with the party's more liberal base, however, Gore initially worked to keep Nader off the ballot in a number of states to prevent voters from even having the choice. And, while Gore was willing to debate Bush, the opponent on his right, he refused to debate his opponent on his left, apparently fearing how voters might react if they were able to compare his positions with those of the well-respected consumer advocate. In the final week of the campaign, recognizing that he was losing liberal voters to his Green Party challenger, Gore did shift the tone of his campaign somewhat to the left, spouting more populist themes. In those final days, polls showed he gained three percentage points, finally pulling slightly ahead of Bush, while Nader dropped from 6% to 3%.
But it was too little too late. So many of us were so disgusted with eight years of center-right governance of the Clinton Administration and the prospects of more under Al Gore, we just could not stomach voting Democratic, even though it was apparent that the election was very close. After eight years of bitter disappointment with Clinton and Gore in power in Washington, it felt cynical and self-defeating to once again vote for a lesser evil, which seemingly would only contribute to the downward spiral which was taking the Democratic Party further and further away from its progressive heyday with the nomination of George McGovern in 1972. In many ways, then, Nader was a symptom, not a cause, of the large-scale alienation with Gore.
The author talks quite a bit about how the decision that eventually ended up with Florida being close enough of a race to be stolen by the Republicans and put Bush in the WH actually caused the Democratic party to move to the right instead of being "taught a lesson"
Unfortunately, following the debacle of the national election of 2000, rather than learn their lesson and move to the left, the Democrats moved still further to the right, with the majority of Democratic senators voting with their Republican counterparts in October 2002 to authorize the fraudulently elected president with the unprecedented authority to invade an oil-rich country on the far side of the world that was no threat to the United states. On the House side, most Democrats voted against authorizing the war, but the most important Democratic leaders sided with Bush as well. Though the party not controlling the White House normally picks up seats in mid-term Congressional elections, as a result of this betrayal of the vast majority of Democratic voters who opposed the invasion of Iraq, millions stayed home, resulting in the Republicans regaining control of the Senate and increasing their majority in the House.
One can also make the case that voting is a sacred right that should not be exercised for strategic reasons, but on moral principles alone. The suffragettes and civil rights advocates who risked their lives for the right to vote were not doing so simply to be able to cast their ballot for a lesser evil. There is a related argument that it is morally and psychologically damaging to compromise one's principles by voting for someone whose policies you don't agree with against someone whose policies you do believe in; that it is important to vote your hopes rather than your fears.
However, the idea that one can "teach the Democrats a lesson" by voting for a progressive third party or not voting at all and thereby allowing Republicans to win just doesn't seem to work.
There is more but this message is already tldr. If interested, the link to the whole article can be found here:
http://www.commondreams.org/views/2010/11/01/my-support-ralph-nader-ten-years-later-lessons-learned
