Today, Hillary supporter David Brock published an open letter at his Correct the Record site. The point of the letter is ostensibly to ask Bernie Sanders to tone down his negative advertising against Hillary Clinton.

I’m writing today to urge that you and your campaign immediately halt all negative campaigning against our party’s prospective candidate for the Presidency, Secretary Hillary Clinton.

After first pledging to wage a positive campaign for President, you and your campaign have for weeks now engaged in a relentlessly ugly barrage of false character attacks against Mrs. Clinton, including running negative TV advertising of the sort you promised you never would…

Your continued suggestions that Mrs. Clinton is untrustworthy and even corrupt – when nothing could be further from the truth – are a threat to our party’s standing, up and down the November ballot.

Attacking Hillary isn’t just politics as usual it’s a threat to the future of the entire Democratic party. Having made clear his desire for Sanders to shut up, Brock turns to his broader purpose, telling Bernie Sanders it’s time for him to fall in line:

With Mrs. Clinton now universally recognized as the leading candidate for the Democratic Presidential nomination, at this juncture, by staying negative, all you are doing is helping Karl Rove and his ilk do their general election dirty work…You can play a constructive role in the party by continuing this substantive dialogue and staying positive for the duration of your campaign.

That’s the real message here: Surrender for the greater good. You had a good run, Bernie, but now it’s time to back off before the real nominee–and the whole party–gets hurt. I’m sure everyone in the Sanders camp is thrilled at this kind of condescension coming from a highly paid Clinton sycophant.

Brock’s Correct the Record is, as of last year, a stand alone super-PAC devoted to defending Hillary Clinton in the media. It was originally an offshoot of American Bridge, Brock’s tracking firm designed to do oppo research and, whenever possible, capture Republicans in embarrassing gaffes. You can think of American Bridge and Correct the Record as the media offense and media defense for Hillary Clinton in 2016.