While Democratic groups politically have proven they can be as dishonest as Republicans at times in their spin and distortions, (when they don't have to) it's left mostly to Republicans to chronically lie about their policies and the provably negative effects these policies have on the country as a whole.
In the past Republicans have both credited and discredit the same agency and their findings depending on whether those findings were favorable to Republican positions and ideology or unfavorable.
During the health care debate, the CBO scored the public option and said that it would actually decrease the overall deficit by $160 billion ( a far cry from the projections of Obamacare, Obama's poor political substitute which will inevitably cost people more).
Republicans were apoplectic since they had staked out a position as deficit hawks and opposed health care reform at the same time and this undermined both positions. So they discredited not just the CBO's numbers but the Budget Office itself as being partisan and unreliable and even incompetent. Except when Republicans regained control of the House, CBO numbers on another issue, favorable to Republicans, were touted by Republicans as accurate and used as a political weapon against Democrats.
Now the New York Times is reporting that Republicans pressured the Congressional Research Service, a non-partisan agency and arm of the Library of Congress, that issued a report that found no correlation between tax cuts for upper income earners and job creation or economic growth, substantially putting the lie to what many already knew -- Republican trickle down economics, the idea they use to justify their tax cuts for the upper 1% of income earners is a fiction and would be the same failure under Romney that it was during the Bush years.
Democrat Charles Schumer pointed out that " they ( Republicans) didn't like the report and instead of rebutting it made them take it down".
Though the research service is non-partisan Republicans protested the reports use of the words " Bush tax cuts", and "tax cuts for the rich" and used that,and charges that those words proved the report was political, as part of the reason they pressured the agency to withdraw the report.
The real reason of course is they don't like what the report says since it undermines every aspect of what was already proven to be a failed economic approach. They also discredited the Tax Policy Center which put out a report that Romney's proposal to cut tax rates 20% while cutting the deficit was mathematically impossible.
No matter what math is used, it all adds up to the same thing - Republican unable to support their ideology with facts, truth, or reality, and try and repress anything that proves their ideology and policies wrong. They have proved in the past they will resort to anything , any subterfuge to try and push their ideology through and what makes their policies dangerous is that they have shown they really don't care whether their ideology solves problems or not -- its the ideology that matters not results.
So anything that discredits their ideology or policies in turn gets discredited by Republicans whether its economics, unemployment ,climate change, or anything else. Which really becomes the best reason in the world for voters to decide this election that its the Republicans and their ways of doing business that no longer matters. And to keep in mind the admonition that those who don't learn from history are doomed to repeat it.