GOP's Relief Bill Won't Be Enough to Prevent Double-Dip Recession: Zandi

More fiscal support is needed because of the "re-intensifying virus" and the continued suffering of American workers who remain jobless or are enduring cuts to pay and/or hours, according to Zandi. "Without additional help they will have no choice but to stop paying their bills and pull way back on their spending," he writes.

That aid, along with more more funds for state and local governments, would provide the biggest multiplier effect for the broader economy, essentially providing more bang for the buck, according to Zandi. Stimulus checks have a smaller impact because higher income households tend to save their checks instead of spending.

State and local governments need more federal aid to avoid potentially millions of layoffs on top of the 1.5 million workers they have already been laid off during the pandemic, which would slow the  national economy even further, writes Dan White, director of government consulting and fiscal policy research at Moody's Analytics, in the firm's macro outlook. 

State and local government budgets are strapped due to reduced revenues and increased spending on services and states' inability to use deficit spending. Unlike the federal government, states must balance their budgets annually, which, in turn, means less funding for towns and cities at times like these.

"If lawmakers fail to come through, the economy is likely to suffer a double-dip recession, with real GDP resuming its decline in their year's fourth quarter and the first quarter of next year," writes Zandi, noting that his outlook assumes no "serious second wave this fall" or an effective vaccine in the interim.

— Check out New GOP Stimulus Package Set for Monday Release on ThinkAdvisor.