70 economists are calling for a large-scale infrastructure investment

• Seventy economists signed onto a new letter saying it's time for a big investment in infrastructure.
• The letter points to President Joe Biden's new infrastructure package, which would cost $2 trillion.
• One economist told Insider that the idea it's "some crazy exorbitant package" doesn't hold water.

Seventy economists have signed on to a letter saying it's time to go big on infrastructure.

"A multitrillion-dollar investment in infrastructure like the one President Biden laid out last week will help pave the way for sustainable and equitable economic growth and pay for itself in the long run," the letter, coordinated by political action group Invest in America, says.

The first part of the package, which President Joe Biden announced last week, will cost $2 trillion. It's wide in scope, divvying out funding from everything from traditional roads and bridges to care workers and universal broadband.

"It's a once-in-a generation investment in America, unlike anything we've seen or done since we built the Interstate Highway System and the Space Race decades ago," Biden said in his speech introducing the package. "In fact, it's the largest American jobs investment since World War Two."

Signatory Dean Baker, a senior economist and cofounder of the left-leaning think tank Center for Economic and Policy Research, told Insider that an infrastructure package isn't needed just now; it's been needed for awhile.

"I think it's very well timed," he said, adding: "Politics doesn't mean you get to necessarily do things at the best time, but this is the time that Biden and the Democrats have to move forward."

The American Jobs Plan has already seen a Goldilocks-esque response. Republicans say it's too big, with not enough spending allocated towards what they consider infrastructure. Some progressives, including Rep. Alexandria Ocasio-Cortez, have said the package should go even bigger.

"You can look at it and say, 'There's more you could do.' And that's true," Baker said. "But I think given political realities, it's taking a really big bite. And my own view is it's really important to sort of get a foot in the door."

The infrastructure package comes paired with the Made in America Tax Plan, which would raise the corporate tax rate to 28% from 21%. It's meant to offset the complete cost of the bill within 15 years. Polling from Morning Consult/Politico found that voters support paying for the package with tax hikes, although they prefer increased taxes on the wealthy more than on corporations.

But the American Jobs Plan still has a long path ahead of it before becoming law. Bipartisan support is looking increasingly unlikely, as Senate Minority Leader Mitch McConnell has said that the current package won't get any Senate GOP votes.

While party-line reconciliation - which was used to pass the American Rescue Plan - may be on the table, even that could get complicated: Moderate Democrat Sen. Joe Manchin has said he wants any infrastructure package to be bipartisan and not passed via reconciliation, although he has said he wants tax hikes included. More recently, he's been more specific about his demands on both counts, indicating compromises are likely to be struck ahead.

That could also prove tricky with the scope of the package, which will come in two parts; Biden is set to announce the next half, focused on childcare, education, and other human infrastructure, in mid-April. Democrats may be able to pass both via reconciliation, as Majority Leader Chuck Schumer has looked into ways that two more reconciliation bills could pass this year.

"The idea that this is some crazy exorbitant package, I mean, that just doesn't hold water. So it's a substantial chunk that will have a very big impact," Baker said. "And, in my view if it turns out - as I think it will - that it's successful in helping to promote clean technologies, people will see that, yeah, this is a good program."