Authors Waggoner and Markowitz.

@algini1 

Actually, it is because the parties look to different modes of fixing the fiscal problems with the Social Security Trust Fund.  

By law, the program may NOT be altered through a reconciliation bill, so 60 votes are required in the Senate, and no party is likely to control that many votes in the foreseeable future.

So any change to fix solvency, to change benefits,  + or -, remove or alter the method used to set the annual tax cap, benefit formula changes, change retirement age, increase rate of contributions OR ANY CHANGE that involves changing one or more of the programs of Social Security - Retirement, including spousal, Survivors or Social Security Disability - must always be done this way 60 VOTES for passage in the Senate.

Brookings,edu 02/11/2025 - FIXING SOCIAL SECURITY 

Why is it critical to revise this vital program? According to the Social Security Administration’s (SSA) Office of the Chief Actuary and the Congressional Budget Office (CBO), the Old-Age and Survivor Insurance (OASI) Trust Fund—the source of the program’s retirement benefits—is forecast to exhaust its funds in 2033. When that happens, the available revenues to the OASI fund will be able to finance about 83% of scheduled benefits. In other words, the resulting gap means Social Security checks for these beneficiaries will shrink by about 17%.

Avoiding that insolvency will require substantial policy changes. The size of the deficit over 75 years—3.5% of taxable payroll, according to the 2024 Social Security Trustee’s Report—is about 1.7 times as large as the deficit the program was facing nearly four decades ago, when Congress in 1983 adopted the most recent amendments to the Great Depression-era Social Security Act. Relying on different assumptions about fertility, immigration, economic growth, and other factors, CBO predicts an even larger deficit over 75 years—4.3% of taxable payroll or more than twice as large as in 1983. Both forecasts make the fundamental point that the Social Security system will not have enough money.

… . . The need to stave off the trust fund’s depletion comes as the Democrat and Republican political parties have sharply divergent views about how to fix the problem. Members of both parties in Congress have recently introduced Social Security solvency plans. The Democratic plans call for restoring solvency entirely by increasing revenue. The major Republican plans would restore solvency entirely by reducing benefits. Both parties have been reluctant to move Social Security legislation because doing so would come with political pain: raising taxes or cutting benefits.