If you've been paying attention to the policy food-fight on Capitol Hill that is the debate over tax reform, then you've probably heard an interesting - and troubling - claim made by U.S. Sen. Bob Casey, D-Pa., and his Democratic colleagues.

Namely, that the tax plan proffered by House Speaker Paul J. Ryan, R-Wisc., and his fellow Republicans would saddle families nationwide, who earn up to $86,100, with an average tax increase of $794.

Casey, of Scranton, tweeted (since deleted) as much on Oct. 24, ditto for Sen. Kamala Harris, D-Calif, who posited that "On average, middle class families earning less than $86,000 would see a tax increase under the Republican 'tax reform' plan," in an Oct. 27 tweet.

Intrigued by the claim, The Washington Post checked the facts, and found they came up woefully short.

Scratch that ... they were a serious whopper.

Here's The Post:

"We traced the talking point to a document put out by the Democratic Policy and Communications Committee, essentially the communications arm of Senate Democrats. That document laid out a series of statistics, tailored for each individual state, that purported to show how damaging the evolving Republican tax plan would be for middle-class Americans.

That document had this line on each state page: "The average tax increase on families nationwide earning up to $86,100 would be $794, a significant burden for middle-class families."

This factoid in turn was sourced to a report by Democrats on the Joint Economic Committee. So we tracked that down.

That report had this line: "If enacted, the Republican tax reform proposal would saddle 8 million households that earn up to $86,100 with an average tax increase of $794 -- a substantial expense for working families."

Note the difference. The original report referred to 8 million households receiving a $794 tax increase. Somehow, when it got communicated down the line, that nuance was lost and it was translated into a talking point referring to all working-class families."

The Joint Economic Committee told The Post that its staff came up with its estimate by running numbers from "the Tax Policy Center, based on the GOP's 'Unified Framework' released in September. The staff then focused on the households making under $86,100 -- the bottom three quintiles of taxpayers -- that would face a tax increase. Weighting the tax increase by the number of people in each quintile, the staff came up with an average tax hike of $794 for the people receiving a tax increase."

As The Post notes, "Only a small percentage (6.5 percent) of the nearly 122 million households in the bottom three quintiles will actually face a tax increase."

And, meanwhile, "more than 97 million (80 percent) will receive a tax cut. Doing the math the same way the JEC staff did, we come up with an average tax cut of about $450 for those 97 million households."

The Post awarded the Democrats' claim its highest (or depending on how you look at, lowest) honor: Four Pinocchios.

As you might expect, Republicans pounced.

Jon Anzur, a spokesman for U.S. Rep. Lou Barletta, one of several Republicans vying for the GOP nomination to challenge Casey in 2018, said in a statement that, "Casey is not only working against Pennsylvania's taxpayers -- he's lying to them too. Pennsylvanians deserve a senator who works for, not against, them. Lou Barletta will always fight to put Pennsylvania workers and families first."