Personally, I think Calexit should be encouraged. I'm thinking of a secession treaty between the U.S. and the Republic of California that would give them a share of the national debt based partly on GDP and partly on population (to top up their own unfunded liabilities, which, them having seceded the rest of us would never have to deal with), require plebiscites in all counties bordering other states to allow them to leave California and join the neighboring state if the majority vote to do so, perpetual leases on our naval bases in CA, a robust free trade agreement (too many supply chains run through CA), and a requirement that they use the U.S. dollar as their currency for a decade and peg their own currency issued after that to the dollar for a period of not less than another decade.
Just think 54 fewer electoral votes locked for the 'Rats, two fewer 'Rat Senators, the heavily 'Rat congressional delegation gone, diminished influence of California lunacy on the rest of the country, and an object lesson in how the left's ideas lead to tyranny and economic ruin when, unrestrained by the U.S. Constitution and the Federal government, California really does go down the path so many of its "lumniaries" are advocating. Sure, at some point, we'd have to reconquer the place to deal with a humanitarian crisis of some sort, but even with that down-side, having them out of the Union for a while would be a great benefit.
Of course, maybe having them leave without a treaty would be better: anyone for a round of radical reconstruction?