Every analysis I read says that Sanders managed to upset Clinton in Michigan because he poured most of his resources there. He could do the same with Ohio but that risks him getting steamrolled in the other 3/15 states.
Sanders could easily spend 40 Mio. $ in the Super 2.0 Tuesday states.
Because afterwards there are only small states for a while and his fundraising would pick up significantly anyway if he does well.
It's not just money. Sanders had camped the entire week in Michigan and held rallies at every university campus in the state. Hard to do the same when 5 big states vote in just one week.
To be fair, Sanders was still doing events in Kansas and Nebraska up until last Friday. He only had 3 days to really blitz Michigan.
He's been in Florida the last two days (Miami yesterday, Kissimmee and Tampa today) as there will be a debate tonight back in Miami. I have to imagine today will be his last day in Florida. I have to imagine his time is going to be spread out pretty evenly between Illinois, Missouri (would love to see a poll from here), and Ohio over the next 5 days. Also I hope he doesn't completely give up on keeping the delegate margin closer in North Carolina. A rally in Asheville and the Research Triangle Area (or just heavily media spending in those areas) could help him not get blown out and maybe he could win some CDs.
Sanders should mostly stay out of FL. It's a trap. It has a very hostile, anti-Sanders electorate (Blacks, Hispanics, old women with a Hillary-fetish etc.) He should really spend more time in the winnable states such as OH and MO and some time in IL and NC instead.
He is in a bind when it comes to Florida. If Clinton wins by 30 points then any eventual win in Missouri or Ohio will be a Pyrrhic one.
Just take under consideration that the delegate margin he accumulated with his 8 wins was wiped out just by her win in Texas.