OK, here's some off-the-cuff advice from an "enemy". What the Donkeys should do is split the party.
Right now retail level US politics has the Donkey party, a strange bedfellows coalition of Librulz and centrists, and the Elephant party for the conservatives. Given the centrifugal forces of our winner-take-all elections, the "compromise zone" is necessarily going to be between the two parties... in other words, at the right-center.
The Donkeys should hive off a "Mules Party".
The Mules would be a modern day fusion party for the Librulz currently in the Donkey party. Here's what Wikipedia has to say about
Fusion Politics. The Mules bylaws would be set up so that (a) the Mules would need an internal supermajority (say 2/3 or 3/4) to nominate a unique Mule candidate, (b) otherwise, in states where fusion is legal, rules would require the Mules to fusion nominate a non-Elephant party candidate, and otherwise (c) in states where fusion is not legal, rules would require that no Mule candidate be nominated, and instead a non-Elephant party candidate be endorsed.
Fusion is currently legal in eight states: California (POTUS BOWL only, 55 electricians), Connecticut (7), Delaware (3), Idaho (4), Mississippi (6), New York (29), Oregon (7), South Carolina (9), and Vermont (3).
For the current staffers with the Donkeys, nothing much changes. They'll still be the ones sucking the $$$$ out of the unions, and the rich, while grooming our best HS debaters for public office. They'll still be the party which proudly stands for nothing, except spineless compromise with the Elephants. But streamlined... as they'll hive off some currently marginalized deadwood, and off-source the bulk of their flesh-and-blood zombie army of volunteers.
The Mules would be staffed by the currently marginalized Librulz clogging up the Donkey's offices, and some "progressive" congress-creatures with dead-end career paths, like B.Sanders y/o E.Warren. They'll also get to be the party that "Stands for Something (trademark pending)". Most importantly, they'd become the locus for relentlessly squeezing free work hours (doing the most mind-numbing and soul-killing tasks, like phone banking), from all the naive volunteers who wanna "Do Something Real (trademark pending)" for a party that "Stands for Something (trademark pending)".
However, on the retail level of US Politics...
Marketingwise, the reorganized Donkey party can rebrand themselves as a centrist party. That should increase their market penetration into the right-center demographic. They also no longer need be worried about the centrist and center-right demographic of their own party defecting to the Elephants because some addled brained Democratic Socialist forgets to mention the "Democratic" part from time to time.
While, the Mules can effectively retain the Librulz demographic of the Donkey party. This would effectively forestall defections of the third party/protest vote kind from that demographic. This, while increasing the effective Donkey market penetration amount Librulz independents. Especially those independents who would prefer a party which "Stands for Something (trademark pending)" as their Hobson's Choice, and those who would prefer not to dirty their hands supporting war-mongering center-right neo-cons... as the Donkeys tend to nominate.
Just my $0.02.