How To Win: Third Party Or Primarying Incumbents?

In case you haven't heard of this yet, there is a divide among progressives as to whether we should try to take over the corrupt Democratic Party through primaries, or whether we should start a third party, either to win the election or spoil the race for the Democrats so much that they're forced to fight for progressive policies. Before I give my take on the issue, I want to make absolutely clear that I welcome any and all peaceful means for progressive change, I'm just trying to figure out which has better odds of success:

If your goal is to spoil the race for the Democrats, that's fairly easy, you probably just need about 5-10% of the previous Democratic vote. You have to consider that good chunk of the voters for a third party will be non-voters who would never vote blue anyway, but you could spoil it if you try, especially with a well-known candidate like Bernie. There's a movement to "Draft Bernie For A People's Party", who say they plan on actually winning.

In that case, you'd need to reduce the Democratic Party to below those 5-10% of the vote, assuming you don't get Republican votes. Based on the 2016 results, even with 5% of the Republican vote, you still need 43.8% of the total vote to win the popular vote, or the Greens' 1% + 42.8 percentage points of Hillary's 48.2%, which would be 88.9% of the Democratic vote. If you think you can win 88.9% of the Democratic vote in the general election, then surely you can win at least a majority in the Democratic primary, right? So why would you refuse to take part in that?

And that's exactly the reason why I support primarying over going the third party route: The vote threshold for winning is simply much lower at 50%, as opposed to roughly 90% for a third party.

Imperical data is also a good argument in favor of primaries: How many third party candidates are there in Congress? 0. The Greens have unfortunately never come close to winning, as much as I support their cause, meanwhile Justice Democrats, a group whose sole purpose is getting uncorrupted progressives elected to Congress, managed to get 4 completely new candidates elected to Congress in their first try in 2018. The most famous of those is Alexandria Ocasio-Cortez, who stunned the world when she beat Democratic incumbent Joe Crowley in a primary with 55% of the vote, the 3rd most powerful Democrat in the House, who was expected to succeed Pelosi as Speaker.

Ultimately, with elected progressive Democrats, we can force incumbent Democrats to adopt our message, for example when Alexandria Ocasio-Cortez uses her publicity to protest for a Green New Deal at Nancy Pelosi's office, who is then forced to agree with that policy or risk losing more of her support with the Democratic base. What really gives me hope is that AOC's popularity with the Democratic base allows Justice Democrats to expand their grassroots network for the 2020 Congressional primaries, leading to even more elected progressives in the House and Senate.

What are your thoughts on this issue?