Sen. Rand Paul briefly speaks to reporters on Capitol Hill.

Highlights The partial shutdown began just after Thursday midnight

Senate expected to pass spending deal in early morning hours on Friday

Last month, government shut down for 3 days over undocumented immigrants

The federal government shut down for the second time in three weeks Friday, driven to the brink by acute congressional dysfunction and pushed over it by the objections of a single conservative senator.The partial shutdown began just after midnight when the government, operating on the latest in a series of short-term spending bills, ran out of money because Congress missed its deadline to pass a new one. But the closure could be brief, with minimal disruptions to federal workers and others.The Senate was expected to pass a massive spending deal in the early morning hours Friday that would reopen the government. The legislation would then head to the House, but the outlook there was less certain because of opposition from liberal Democrats and conservative Republicans, and quick passage was not assured.In a brief interview with The Washington Post, White House legislative affairs director Marc Short said the administration was preparing for the possibility of a temporary shutdown, perhaps spanning a few hours.Last month, the government shut down for three days in a dispute over undocumented immigrants brought to the country as children, reopening after Senate Democrats accepted assurances from Senate Majority Leader Mitch McConnell, R-Ky., that he would hold a floor debate on immigration this month.The latest congressional breakdown came amid disputes over a massive bipartisan spending deal that would shower hundreds of billions of dollars on military and domestic programs alike, lift the federal debt limit for a year and speed disaster aid to hurricane-ravaged areas.Earlier in the week, the legislation had appeared primed for easy congressional passage, as McConnell and Minority Leader Charles Schumer, D-N.Y., unveiled it jointly on the Senate floor Wednesday with a bipartisan flourish and mutual praise.But it began to run into trouble Thursday as House conservatives rebelled over excessive deficit spending and House liberals fumed that this bill, too, failed to protect "dreamers" who face losing deportation protections under the Trump administration.Then, as an expected vote approached in the Senate, Sen. Rand Paul, R-Ky., began to throw up roadblocks, demanding a vote on an amendment that would demonstrate how the two-year budget deal breaks past pledges to rein in federal spending.GOP leaders refused to allow him to offer the amendment, arguing that if Paul got an amendment vote many other senators might want one, too. Paul, in turn, refused to allow the vote to go forward, making use of Senate rules that allow individual senators to slow down proceedings that require the consent of all."I can't in all good honesty, in all good faith, just look the other way because my party is now complicit in the deficits," Paul said on the Senate floor as evening pushed into night.Paul objected after a visibly irritated McConnell tried to move to a vote. Then Paul launched into a lengthy floor speech deriding bipartisan complicity on deficit spending while the country goes "on and on and on finding new wars to fight that make no sense." The senator direly predicted a "day of reckoning," possibly in the form of the collapse of the stock market.As the hours ticked on, Paul repeatedly refused to consent to allowing the vote to happen, as lawmakers and aides grew increasingly annoyed at him. Sen. John Cornyn, R-Texas, leaving the floor after an unsuccessful attempt to curtail Paul's standoff, called the gambit "grossly irresponsible" and said that leaders would not entertain his demand for a vote."Why reward bad behavior?" Cornyn said.Senate leaders remained confident the spending deal would pass easily in the end. But absent an agreement among all senators on timing, the first votes were delayed until 1 a.m., when time allotted for debate would expire. Final passage was expected some two hours later.Meanwhile even bigger problems appeared to be surfacing in the House, where liberals led by Minority Leader Nancy Pelosi, D-Calif., were incensed that the plight of young undocumented immigrants who face the threat of deportation was not addressed in the spending bill.Pelosi planned to vote against the bill. And despite initially suggesting that she would not be urging fellow Democrats to follow her lead, she increasingly appeared to be doing exactly that.At a closed-door evening meeting of House Democrats, Pelosi told lawmakers: "We have a moment. They don't have the votes. All of us should use our leverage. This is what we believe in," according to one House Democrat in the room, who spoke on the condition of anonymity to disclose the private conversation.Pelosi is under intense pressure from immigration activists and liberals in her caucus to take a stand for the "dreamers" - undocumented immigrants brought to the country as children who face losing work permits granted by President Barack Obama under the Deferred Action for Childhood Arrivals program (DACA) but rescinded by President Donald Trump.Supporters of these immigrants have watched in growing outrage as Democrats have failed repeatedly to achieve results for the cause. They want to see Democrats stand strong, even after last month's shutdown failed to achieve more than a commitment from McConnell to hold a debate.But many House Democrats are skittish over forcing another shutdown, especially with Senate Democrats largely on board with the spending deal.Several Democrats emerged from the more than hour-long caucus meeting insisting that there was not a firm effort by party leaders to oppose the bill and perhaps force a shutdown. But many appeared resolved to hold the line against any deal that did not address the party's immigration concerns."I think there's a very strong sentiment that this is a moment that we can't let pass," Rep. Daniel Kildee, D-Mich., said. "We've allowed these moments to pass in the past. This is a moment we can't let pass without doing everything we can to move forward on DACA. And all we're looking for is a simple statement from (House Speaker) Paul Ryan."Others were unconvinced.Rep. John Yarmuth, D-Ky., the top Democrat on the House Budget Committee and a supporter of the deal, said the outcome may well depend on forces out of the House Democrats' control - such as how many Senate Democrats end up voting for the bill and how many House Republicans support it."If Republicans had 70 votes and needed 140 from us, then there's no pressure on us, because then it's their fault," Yarmuth said. "But if they have 170 and we can't put up 40 to support a bipartisan bill coming from the Senate, then we get blamed for a shutdown."House conservatives were also balking, objecting to the enormous increase in federal spending, most of which would be piled onto the deficit with minimal attempts to offset it.Earlier Thursday, Ryan expressed confidence that the bill, which delivers a military funding boost sought by the GOP alongside increases in domestic spending favored by Democrats, would pass. "There is widespread agreement in both parties that we have cut the military too much, that our service members are suffering as a result, and that we need to do better," he said.But the outlook grew cloudier as the evening wore on.If the larger spending bill does pass, its impact would be wide-ranging - renewing several large health-care programs, suspending the national debt limit for a year and extending billions of dollars of expiring business tax breaks. The cost of those provisions exceeds $560 billion, though lawmakers included some revenue-raising offsets, such as increases in customs fees and a sell-off from the Strategic Petroleum Reserve.In comparison, the 2009 fiscal stimulus bill passed at the bottom of a global recession under Obama was estimated to cost $787 billion over 10 years. Republicans were nearly unanimous in opposing that measure in their clamor for fiscal restraint in the face of growing deficits - demands largely drowned out now in the Trump era.This spending bill, proposed amid an economic boom, could be the last major piece of legislation passed before November's midterm elections, barring a breakthrough on the thorny immigration debate.Under the deal, existing spending limits would be raised by a combined $296 billion through 2019. The caps were put in place in 2011 after a fiscal showdown between Obama and GOP congressional leaders, who demanded spending austerity.- - -

The Washington Post's Ed O'Keefe and Damian Paletta contributed to this report.