On the first day of the congressional session in January, senators and representatives recited this pledge:

"I do solemnly swear that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter: So help me God."

That's the one and only pledge they ought to take with regard to serving in Congress.

Yet it's become increasingly common for myriad special interests to pressure candidates and even elected officials to swear allegiance to their particular cause, to demand that they commit their votes regardless of what facts and circumstances may surface later.

Best known is the no-new-taxes pledge championed by Republican lobbyist Grover Norquist that has needlessly complicated budget and debt-reduction talks in Washington for years. On this page, we also have criticized a pledge proffered each election cycle to candidates seeking the endorsement of the Service Employees International Union, which represents thousands of public employees.

There's a new pledge making the rounds. Drafted by Reps. Alan Grayson and Mark Takano, it calls on fellow House members to promise to "vote against any and every cut to Medicare, Medicaid or Social Security benefits — including raising the retirement age or cutting the cost of living adjustments that our constituents earned and need."

There's a special effort to get commitments from members of the Congressional Progressive Caucus. Among them is the North Coast's new congressman, Democrat Jared Huffman of San Rafael. He is one of 49 who haven't signed. "I won't be bullied from the left or the right into signing Norquistian vote pledges to outside groups," he wrote on his Facebook page.

Among those pushing the pledge is Norman Solomon, a Marin County journalist and political activist who ran for Congress in 2012 and is believed to be mulling whether to challenge Huffman next year.

"In effect," Solomon wrote in a recent column, "their message is: We like to call ourselves 'progressive' but we refuse to clearly stand up to an Obama White House that's pushing to slash Social Security and Medicare benefits."

We oppose pledges as a matter of principle. We think principled lawmakers should weigh all sides of an issue and then decide, not the other way around.

On the particulars, this misguided pledge is a virtual bookend for the Norquist no-taxes pledge.

Revenue and entitlements, along with defense spending, are the primary factors of the debt and deficit equations that Congress, so far, has avoided solving. All three must be on the table in any serious negotiations.

When those talks take place, Huffman and his fellow progressives can and should protect the interests of seniors on Social Security and Medicare and anyone covered by Medicaid without signing a pledge that bars them in advance from bargaining.

If the big issues get taken off the table in advance, the only thing guaranteed is failure.