From an article by Philip Joyce (UMD):

…And CBO Directors—all of them—have always known that when their analyses throw cold water on particular proposals, the people who support those proposals will fire back. It is the fact that CBO has built up credibility over its half century that makes those individuals feel that they must come up with reasons why CBO numbers should not be trusted.

There are two aspects of the current attacks on CBO, however, that are relatively unusual and highly unfortunate. The first is the suggestion that CBO staff are politically biased, with the evidence provided being that some CBO staff, over the past 25 years, donated to Democratic candidates or left-leaning organizations. The significance of this claim was thoroughly debunked by the Washington Post fact-checker. Moreover, there are substantial formal and informal checks aimed at preventing political bias from influencing CBO analyses. In fact, the statute that set up CBO explicitly states that CBO staff are to be hired “without regard to political affiliation,” and the culture established by Alice Rivlin consistently reinforces its nonpartisan ethic. And it is important to note the difference between being nonpartisan and “bipartisan”; the former means that you are not allowing political considerations to influence your work, while the latter involves seeking cooperation between two political parties. It is an insult to these hard-working, committed professionals to suggest that they are somehow trying to make policies of a particular party, or a particular President, harder to achieve because of some political bias.

The second is that increasingly many of these criticisms of CBO are coming not from the executive branch, but from inside of the Congress. These include both factual misrepresentations (such as the claim that CBO understated the revenue effects of the 2017 Trump tax cuts, when the difference was entirely related to COVID-era inflation that was unanticipated by everyone) and attacks on the legitimacy of CBO itself. Of particular concern is the general lack of support shown by the Budget Committees, who have in the past generally risen to the defense of CBO in the face of executive branch criticisms. What makes the lack of Congressional support so unfortunate is the potential effect that it could have on the budgetary separation of powers. Weakening the CBO weakens Congress. Even a partisan Republican should understand that the aspects of CBO analysis that constrain a Republican President also limit overreach by a Democratic president. When the political winds change, they will need the CBO’s credibility to allow the Congress to effectively challenge future policies.

If Congress wishes to remain strong as an institution, and to continue to be able to play its constitutional role of being able to challenge the executive branch when it disagrees with its policy proposals, it needs the capacity for analysis, and the credibility, that CBO has earned over the years. Blithely attempting to toss that away in the interest of short-term policy gains is both ill-advised for the Congress and dangerous to democracy.

Entire article here.