The Brookings report is based on past CBO analyses of policies included in the new GOP bill, all of which are predicted to cause people to lose their insurance coverage. These policies include repealing Obamacare's individual mandate that everyone must purchase some form of health insurance, changing Medicaid into block grants to states on a per capita basis, replacing the current Obamacare subsidies with less-generous tax credits, and allowing insurers to charge people higher premiums if their coverage lapses for more than 60 days.

Though they predicted a potentially less catastrophic outcome than Brookings, Standard & Poor’s also estimated in a report this week that millions will lose coverage under the Republican plan. The ratings agency predicts that two to four million people would drop out of the individual insurance market due to rising premium costs, and that another four to six million would lose their Medicaid coverage.

The authors of the bill, when asked directly this week if it will cause people to lose their health insurance, have refused to answer.

Ahead of the CBO's likely gloomy report, which could come as soon as next week, Republican lawmakers and the White House have worked to erode the public's trust in the office, calling its work "inconsistent," and "way off," and accusing them of having "scored everything wrong for decades."

Republican members of Congress told TPM that will instead rely on their own internal analyses of the bill, backed up by "some spreadsheets or whatever."