It seems like the main response to my claim that Sander's path to the nomination is quite narrow notwithstanding the fact that he received a plurality of the votes in the only two states to vote so far is something along the lines of "what about Trump in 2016?" While I really hate the Trump-Sanders comparisons (Sanders is not the Democrats' Trump for a bunch of reasons), it is true that at this stage in the 2016 primary, it looked like Trump only had support of about a third of the Republican primary vote. So if he ended up with a majority of delegates in the end, why can't Sanders do the same thing?
The reason why is because the Republicans primary runs on different rules than the Democratic primary. While the Democrats assign delegates proportionately, the Republicans mostly use a winner-takes-all system (meaning whoever gets the most votes is assigned all the delegates for the state). Look at the results of the Florida primaries in 2016, for example. Trump received 45.7% of the vote there, but was awarded all 99 delegates. Meanwhile, Clinton received 64.4% of the votes and was allocated 141 of the 214 delegates at stake, which is roughly 65% of the delegate total for the state.
Because the parties use different systems, it is much more likely that Democrats will end up with a contested convention that Republicans. Trump could have won a clear majority of the delegates before the convention with only 35% of the vote as long as all of his competitors usually got a lower percentages than he did. If Bernie consistently gets 35% in the current contest, he will end up with roughly 35% of the delegates even if Bernie is always the top vote-getter, with the remaining 65% held by anti-Sanders candidates. The path that Trump used to clinch the nomination in 2016 is not available to Democrats.
For the Democrats to avoid a contested convention, they need either for the contest to become a two-person contest relatively early (as it was in 2016) or to have one candidate dominate all the others through most of the primary fight. For Republicans to avoid a contested convention, they just need one candidate to get more votes than the others in enough delegate-rich states even if that one candidate never comes close to a majority. Because of that difference, Sanders probably won't be able to clinch the nomination before the convention, but he can get enough to force a contested convention. Given the Sanders' people's relationship with the other campaigns, unless they start building bridges soon, I don't see how Sanders wins at the convention.
