Some GOP senators want a $50,000 income cutoff for a fresh wave of stimulus checks. That may exclude at least 29 million families who would get one under the Biden relief plan.

• Millions could be left out of receiving a stimulus check under the GOP plan compared to the Biden relief plan.
• Estimates range from 29 million to 36 millions households that could be left out, according to several experts that Insider spoke to.
• "In the near-term that's potentially many thousands of dollars of difference to their budgets," one said.

A group of Republican senators unveiled a $618 billion stimulus counteroffer on Monday. They're aiming to push President Joe Biden into reducing the size and scope of his proposed $1.9 trillion emergency spending package.

The Republican blueprint would significantly cut spending on many programs, including a fresh wave of stimulus payments for Americans. It would distribute $1,000 checks instead of the $1,400 that Democrats envision, and tighten the income parameters significantly.

Under the GOP plan spearheaded by Republican Sen. Susan Collins, the eligibility thresholds are capped for individuals earning $50,000 and couples making $100,000.

Meanwhile, the Biden proposal begins phasing out stimulus checks for individuals making $75,000 and couples earning $150,000 a year.

Several economists have already begun calculating how many fewer families could get a federal check under the GOP plan by comparison. Here are three preliminary estimates from experts:

• 36 million fewer families (Ernie Tedeschi at Evercore ISI)
• 36 million fewer households (Steve Wamhoff at the Institute of Taxation and Economic Policy)
• 29 million fewer families (John Ricco and Victoria Ossorio at the Penn Wharton Budget Model)

The experts cautioned they are early figures because the 10 Republican senators hadn't drafted a bill yet.

Wamhoff at the ITEP broke down his projection further into the number of adults and children, which is different from the number of tax-filers shown above. He estimates around 160 million adults and 66 million children would receive a check in the GOP plan.

That's in stark contrast to the 219 million adults and 89 million kids who qualify for a payment in the Biden plan. Put another way, 80 million fewer people would receive any cash payment in the plan unveiled by the Senate Republicans.

"The GOP plan would exclude more people than the Biden proposal," Ricco, senior analyst at Penn Wharton, said in an interview. "In the near-term that's potentially many thousands of dollars of difference to their budgets."

The Republican proposal illustrates the strong debate on Capitol Hill over the composition of a third wave of stimulus checks. Some senators in both parties are suggesting tightening eligibility for a fresh wave of stimulus payments. It's divided economists as well.

"On the one hand, there are programs that as a first line of defense are better-targeted than checks," Tedeschi said, pointing to unemployment insurance, a safety net program that provides benefits to people who lose jobs. "And if you have any blanket eligibility criteria for checks, there's going to be some people who get it that arguably don't need them."

Biden said recently he is open to adjusting thresholds on the direct payments, though a top White House economist said Monday the administration does not want to curtail them as much as Republicans want.

A new analysis from the Opportunity Insights project indicated that consumer spending didn't budge for people earning above $78,000 last month after they received a $600 stimulus check. Instead, many saved it, suggesting the cash wasn't critical to plug a holes in their budget.

Still, experts like Tedeschi and economist Claudia Sahm say that many people have been locked out of receiving unemployment benefits because of massive backlogs or other administrative problems at state labor offices. Others also argue that people have suffered major pay cuts because of the pandemic.

"One of the advantages on checks is that it fills in the gaps in our safety net by reaching families who have extenuating circumstances that make them ineligible for relief programs," Tedeschi said.