Politico has a very interesting story this morning that gave voice to what a lot of progressives in Washington have been nervously worrying about: the possibility that a freshly re-elected President Obama could sell his base down the river only weeks after the election during fiscal cliff negotiations. (Liberals fear grand bargain betrayal if President Obama wins.)

The concern is that he tried it before: Obama reportedly offered House Speaker John Boehner a deal during the debt ceiling negotiations that would have made all Bush tax cuts permanent while also raising $800 billion in additional tax revenue, and also cut both Medicare and Social Security benefits. Just last month, he told the Des Moines Register editorial board that “I am absolutely confident that we can get what is the equivalent of the grand bargain that essentially I’ve been offering to the Republicans for a very long time.”

Optimists would point out that Obama has nevertheless taken a much more progressive approach since the dark days of the debt ceiling debacle. He released a debt plan last year that was much, much better than what he offered Boehner—it repealed Bush top tax rates and largely stayed away from safety net benefit cuts.

But ultimately, Obama cannot implement a deal alone. He has to get members of his own party to vote for it in Congress—so regardless of the president’s disposition, there are many pressure points in Congress for progressives who want to keep Democrats from cutting the safety net.

To that end, the Progressive Change Campaign Committee has been seeking out Democrats running in tough races and getting them on board with a no-cuts agenda, in exchange for valuable financial and logistical support.

At least eight House candidates are receiving PCCC support, along with four Senators or Senate candidates: Sen. Sherrod Brown, Elizabeth Warren, Tammy Baldwin, and now Representative Shelley Berkley, whom PCCC endorsed on Monday.

On a call with volunteers this week—joined, quite notably, by Senate Majority Leader Harry Reid—Berkley re-stated her position on safety net cuts:

“As far as Social Security, my opponent is on record as wanting to privatize Social Security. I am opposed to that. There is a reason that FDR passed Social Security in 1935. That’s because older Americans, after they retired, they had no income, no way to survive, and their life expectancy was cut short. Same thing with Medicare. There was a reason in 1965 that we passed Medicare. Older Americans were dying and it wasn’t of old age. They were dying for lack of healthcare. So now we’ve created Medicare, created Social Security, I am going to stand and fight for both of these programs. They are very important to seniors and future generations of seniors.

I will promise you without fear of contradiction, I will do everything in my power to strengthen and protect Medicare and Social Security and it’s going to be a cold day in the middle of August in the Nevada desert before I do anything that’s going to harm those two essential programs.”

PCCC has provided 433,000 volunteer calls in support of their Senate candidates and raised over $1.3 million for them. MoveOn and the AFL-CIO are also organizing around a progressive grand bargain push. This is all crucial, because a massive, $30 million “Fix the Debt” campaign, backed by Wall Street money, will be pushing hard from the other direction.