In the 2010 campaign, Republicans vowed to end the long congressional tradition of allowing members to attach unrelated bills onto "must-pass" legislation.

We have not previously rated this campaign promise, which was part of the GOP Pledge to America. But readers asked us to take a look at it in light of end-of-the-year passage of a law to extend the payroll tax cut and unemployment insurance.

The Social Security payroll tax cut had been scheduled to expire Jan. 1, 2012, and the bill adopted in the scramble to extend it not only included the payroll tax and unemployment insurance extensions, but also a 60-day deadline for President Barack Obama to decide whether to approve construction of the controversial Keystone pipeline and a provision preempting the Environmental Protection Agency from applying pollution standards to industrial boilers. Those provisions were added at the behest of House Republicans.

When POLITICO wrote a story in December, suggesting that this action ran afoul of the Republican promise, Michael Steel, a spokesman for Speaker John Boehner, R-Ohio, said the bill "does not fit the definition of 'must-pass' legislation," which he noted generally refers to funding bills or increasing the debt limit, nor did it contain unpopular provisions, he said.

We asked congressional analysts how they defined the term.

"Obviously appropriations bills are the highest order of must-pass bills," said Donald Wolfensberger, director of the Congress Project for the Woodrow Wilson International Center for Scholars. Appropriations bills "have always been rife with legislative riders, no matter which party is in the majority," he said.

"Whether the payroll tax holiday extension bill should be considered 'must pass,' technically it is not the same as an appropriations measure or debt limit bill," he wrote in an email. "It falls more in the category of a 'political should pass bill,' especially going in an election year. You don't cut off unemployment comp to the unemployed or middle class tax cuts on Christmas Eve."

When it comes to appropriations bills, recently passed legislation has contained riders, including measures pushed by Republicans. For instance, both a continuing resolution for fiscal year 2011 and the omnibus spending bill for 2012 (which included what normally would have been nine separate appropriations measures) included prohibitions on the District of Columbia using local funds for abortions. And the 2012 measure included a ban on enforcing light bulb energy efficiency standards set in previously adopted legislation.

"Such policy provisions are a routine part of the Appropriations process and have been for many years under both political parties," said Boehner's spokesman Steel.

Steve Ellis, a vice president at Taxpayers for Common Sense, also said more he viewed the appropriations measures as policy riders rather than an example of packing unpopular bills with "must pass" legislation. As for the Keystone pipeline measure, Ellis noted that it probably would have been popular in the House although perhaps not in the Senate

"It's a really squishy promise," he said. "What is must pass? Is it something that's going to expire? And what is unpopular?" Because of that squishiness, "it's kind of hard to prove that they kept it or broke it."

Norman Ornstein, a scholar at the conservative American Enterprise Institute, told us by email that he would consider all three pieces of legislation, including the payroll tax extension, "'must pass' but in narrow terms, the (continuing resolution) and spending bills are slam dunks for that definition. And clearly, each of the riders were unpopular and controversial provisions intended to force the administration and Democrats to swallow poison pills," he wrote. "So these do violate the pledge."

We agree with Ellis that "must pass" and "unpopular" might be defined differently by different observers. But we think the thrust of the promise was not to throw unrelated items that might not pass on their own into bills that were being taken up with urgency. We rate this a Promise Broken.