Congress has until midnight Sunday to pass a budget, or risk a lapse in spending that could mean furloughs for workers, the expiration of some benefits, delays in travel, and park closures.
In Philadelphia, that could mean that many historic sites around Independence Mall will be closed starting Sunday.
"It'd be a bummer if you got here and couldn't visit any other sites," said Walt Podesta, who was visiting the city with his wife, Barbara, from Sacramento.
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"I think they need to do their job," he said of the government. "That's what they're getting paid for and they're making it more of a political issue."
They're a few of the millions of people who visit the historic mall each year, but the impact of the shutdown will go far beyond tourism woes in the city.
"It'll get worse as it gets longer, I guess, the question is whether it's going to be an immediate impact," said Michael Sances, an associate professor of political science at Temple University.
How did we get here?
Earlier this year, a group of Republican hard-liners in the House refused to raise the nation's debt ceiling until President Joe Biden and the Democratic-controlled Senate agreed to steep spending cuts.
The threat of economic calamity forced Biden to the negotiating table with Speaker Kevin McCarthy, and the two agreed to a spending cap for the upcoming 2024 budget year, which begins Oct. 1. But as the months passed, spending legislation remained mired in Congress with the hard-liners in the House insisting on curbing spending further and other proposals that couldn't pass the Senate.
This week, McCarthy and other House Republicans said they want Biden to agree on border restrictions.
McCarthy rejects Senate spending bill while scrambling for a House plan that averts a shutdown
"If he wants to keep the government open, he needs to shut down the border," Rep. August Pfluger, R-Texas, said of Biden. "No border security, no funding."
That idea is unlikely to survive with even the top Republican in the Senate -- Mitch McConnell of Kentucky -- scoffing at the idea, noting that a shutdown would yank pay from border patrol officers needed for better security.
What happens to Social Security in a shutdown? How will a shutdown impact me?
As disruptive as shutdowns can be to families of government workers -- and cost taxpayers more money in the end -- most Americans won't see a big difference right away.
That's because the vast majority of government spending is set on autopilot by Congress and will continue as "mandatory" spending. Also, hundreds of thousands of government workers will agree to show up without pay -- at least initially.
For example, payments from Social Security, Medicare and Medicaid will continue to reach mailboxes, although agencies warn services could slow down.
At the Social Security Administration, for example, officials say they will continue to ship out payments and people can still apply for benefits. But benefit verifications will stop, and people won't be able to receive replacement Medicare cards.
You should still plan on paying your taxes, but the IRS warns it will be responding to requests with only one-third of its staff.
The U.S. Postal Service also won't be impacted because it relies on its own revenue stream.
For the 27% of government spending that will be impacted, some critical programs such as disaster relief will limp along as government agencies move around cash. Another federal program that provides food assistance to low-income families called SNAP, should be available without problems through October. However, another program by the Agriculture Department that helps feed low-income mothers called WIC could run out of cash within days and waitlists could grow.
To most middle-class Americans, the most obvious impact will be at national parks and federal landmarks, which will close unless state governments pay to keep them open. The Smithsonian buildings and its National Zoo will also close, and the zoo will turn off its "Giant Panda Cam," where Americans can watch the pandas play.
NASA will shutter its public television and coverage of live launches.
Trash could pile up in the federal parks outside the White House, Capitol Hill and other federal buildings, where janitors working for hourly wages under federal contracts will be sent home without pay.
Lawmakers will still take in their $174,000 annual salaries, but their staffs won't get paid, and Republicans won't be able to continue their impeachment inquiry into President Biden.
But the biggest impact will likely be on low-income families outside Washington, where 85% of federal workers live and work. If the shutdown lasts long enough, federal workers and contractors are likely to show up at food banks as they did in the last shutdown five years ago.
SNAP, WIC benefits in Pennsylvania
Sances says people's wallets will suffer, especially those who benefit from grocery assistance programs like WIC and SNAP.
SEE ALSO: These federal programs would be impacted first in a government shutdown
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"WIC is in more danger because it falls into the category of what's called discretionary spending, which means Congress has to vote on it every year. And if Congress doesn't pass a budget, the money just runs out," said Sances.
Data from the House Budget Committee says if this shutdown happens and lingers, 1.9 million Pennsylvanians could lose access to SNAP benefits and nearly 180,000 residents could lose WIC benefits.
"You struggle with other entities of life, work, or other people, daycare," said Tracy Walton from Atlanta.
As a former government employee, she remembers the last shutdown. As someone visiting Philadelphia, she worries about the impact on travel.
Airport impacts
Longer lines at the airport and canceled flights are a possibility too if federal workers who direct traffic or screen luggage quit because of financial troubles and get jobs elsewhere.
TSA employees are federal employees. As the 2018 shutdown dragged on, as many as 10% of workers either called out or stopped showing up since they weren't getting paychecks.
At Pennsylvania airports, more than 35,000 passengers a day could be affected by potential TSA delays.
Lashanda Palmer, who is a TSA officer and mother of five, is beyond frustrated.
She says she survived several government shutdowns, including the last one in 2018. That went on for 35 days.
"We have officers who lost their places of residency, lost their cars. We got people who can't pay to come across the bridge, they can't pay for childcare," said Palmer.
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"I actually hadn't thought about that at all, so now I'm going to have to think about that," said Joe Trimolbi from Tampa.
What happens next?
One possibility is that McCarthy turns to Democrats to help him pass a spending bill, but that's unlikely. Leaning on Democrats would anger hard-liners in his party and possibly trigger calls to oust him as speaker.
More likely, a significant portion of the government will run out of money at midnight on Saturday, and some 4 million workers will stop getting paid, including military troops.
With a shutdown appearing imminent, federal agencies on Thursday notified employees that it's possible they will either be "furloughed" -- a government term for being laid off temporarily -- or "excepted" and required to report to work without pay.
Excepted workers are those needed to protect life and property, including law enforcement and military troops, but also civilians who tend to orbiting space craft, the power grid, federal prisons and airport security.
If a shutdown continues, the first possible missed or incomplete paycheck would be on Oct. 13 for many workers.
All federal workers are expected to get back pay when the shutdown ends, although union officials say that's not a good solution. In the last shutdown, air traffic controllers and security workers began calling in sick because they could no longer afford child care, gas and other expenses to get to work.
Many federal contractors such as janitors and security guards will be laid off too, without the promise of back pay.
How long it could last depends entirely on the House and Senate getting the budget done.