The tactic is not unheard of. In fact, Democratic senator Claire McCaskill deployed the same strategy masterfully when she inserted herself into the 2012 Republican Senate primary with ads calling once-longshot Todd Akin "too conservative" while highlighting his right wing credentials to a right wing Republican base in Missouri. It worked, notes Steve Benen, as Akin won the primary and royally lost to McCaskill in the general election.

This type of advertising has advantage beyond the content of the messages in the ads: it allows both the beneficiary and the benefactor to claim mutual contempt, however thinly veiled, thereby escaping accountability. Because they are technically tagged as spending "against" a campaign rather than for, they are harder to track as outside spending actually in favor of the candidate. This allows Bernie Sanders to claim to be against the billionaire class all the while gladly accepting their dirty money to promote himself with a wink and a nod.

Why are these groups being suddenly so helpful to Bernie? If Bernie Sanders himself is to be believed, they certainly don't want a President Sanders, though they might be quite content with a candidate who, for all his bluster, has proven an ineffectual legislator. But the larger truth is that Bernie Sanders is the candidate Republicans want to run against in November. With their party increasingly likely to nominate an extremist, their only safe bet is to get the Democrats to nominate an extremist as well, if only to "even" the odds.

Hillary Clinton is the most vetted candidate in the history of presidential races, with the possible exception of Barack Obama, who had every stone in his life turned over for the crime of running for and being president while back. Bernie Sanders can't even hold up to the minor vetting of the primary process before we find out that his legislative record is replete with attempting to dump nuclear waste on a poor Latino community, voting with Republicans to protect gun-touting racist thugs on the US-Mexico border... and naming post offices.

Bernie Sanders gets visibly irritated and threatens to walk off the stage with activists trying to draw attention to the important issue of black lives, then trivializes the issue. Hillary Clinton sat in the line of fire of trumped up Benghazi charges from Republicans for 13 straight hours without breaking a sweat.

The Republicans know that polls done on the general election in the midst of primary season are meaningless. The general election campaign determines the outcome of the general election. They have a problem when it comes to that with Hillary Clinton. They have publicly aired and attacked Hillary Clinton with every single thing they have, and she's beaten all of them. Everything they can throw at her in the general election will be old story and therefore less effective.

But for Bernie? You have not yet seen the right wing morph his face into Stalin, Fidel Castro, or Hugo Chavez for being a socialist. You have not yet seen the Republicans go after him for being an out-of-touch tax-and-spend Vermont liberal. You have not yet seen them use the failure of single payer in Vermont and tie it around Bernie nice and tight.

You have not even seen the tip of the iceberg of the Republicans' opposition research on Sanders. They will put together an effective destruction campaign before Bernie has a chance to spell "democratic socialism." They will not just destroy Bernie Sanders; they will link every vulnerable Democrat to him in every conservative or moderate state and district and take them down too (how will a "how can you defend Obamacare when even your party's socialist nominee thinks it's so bad it should be replaced?" question work out for a vulnerable Democrat?).

And what will happen when the Republicans win against Bernie? They will be immediately able to claim a mandate to not just reject ideas to expand the social safety net but also justification to roll back progress we have already made: to abolish Obamacare, to privatize Social Security and Medicare, to roll back banking regulations, to bust unions, to tear apart immigrant families, to deport DREAMers, to grant police carte blanch to shoot unarmed black kids, to cut taxes on the very wealthy and to raise them on everyone else.

Bernie Sanders is the dream Democrat Republicans have been looking for. A Sanders nomination will hand the GOP their wildest goals, not just politically but in public policy. It is their best opportunity to roll back both liberal policies and liberalism 50 years or more.

No wonder the hedge fund managers and investment bankers are working hard for Bernie.