Casey obliged - and his likely 2018 opponent, recruited by Trump, wasted no time accusing him of voting to "put illegal immigrants over health insurance for our kids."
But Casey scoffed at the barb, accusing Republicans of cynically adding an extension of the Children's Health Insurance Program to the bill for political leverage - all for a spending deal that doesn't provide a long-term road map for military spending, the opioid crisis or "dreamers," the young immigrants brought to the United States illegally as children.
"They don't give a damn about these kids," Casey said. "If they gave a damn, they would have gotten it done in September, or October, or November, or December ... now, suddenly, they have a newfound love for CHIP?"
As the blame game launched following the shutdown of the U.S. government at 12:01 a.m. Saturday, it quickly and ferociously began playing out on perhaps the most contentious battlefield of the 2018 midterms: the Senate races where Democrats are seeking re-election in states that Trump won.
Six such Democrats voted against the spending bill in the Senate late Friday. But the vote divided the party, with five Senate Democrats, all from Trump states, voting to avoid a government shutdown - and setting up a fight over what Republicans have tried to brand "the Schumer Shutdown," after Senate Minority Leader Charles E. Schumer, D-N.Y.
At 12:38 a.m. Saturday, the National Republican Senatorial Committee sent out an email blast against Casey, whose leading opponent, Rep. Lou Barletta, is considered a top prospect for helping the GOP pick up a Senate seat.
"Bob Casey had to choose between doing what's best for Pennsylvania and playing partisan games, and he chose the latter," NRSC spokesman Bob Salera wrote in the blast. "By voting against extending CHIP, critical funding for our troops and programs families rely on, Casey is once again proving that his loyalty lies with his liberal colleagues in Washington, not with Pennsylvania."
The NRSC sent a nearly identical attack against Sen. Sherrod Brown, D-Ohio. And Debbi Stabenow, D-Mich. And Bill Nelson, D-Fla. And Jon Tester, D-Mont. And Tammy Baldwin, D-Wis.
And even before the vote Friday, the American Action Network, a group aligned with House Speaker Paul Ryan, R-Wis., announced a national TV ad buy accusing "the Pelosi liberals" of "jeopardizing funding for our troops and jeopardizing funding for health care for millions of American children."
Democrats, who knew the attacks were coming, have responded with videos and online ads that point to the president's 2013 and 2017 quotes about how a shutdown might be good for Republicans. Priorities USA, a Democratic super PAC, started a seven-figure digital ad buy targeting swing seats, showing images of foreign threats and worried families.
"What's President Trump up to?" asks a narrator in the ad. "He says our country needs a good government shutdown."
Yet some Democrats also quietly conceded that the impasse - if it is seen as a fight over immigration - holds risks for vulnerable senators, even if they voted to keep the government open.
One worrisome data point: A super PAC allied with Senate Democrats commissioned a poll in 12 battleground states in early December 2017, and it found that in more conservative states, blame for a shutdown would be split between Trump and Republicans and Democrats in Congress. But when interviewers asked respondents about a shutdown that might be tied to the legal status of dreamers, Democrats absorbed more blame.
The poll was conducted by Garin-Hart-Yang Research Group on behalf of Senate Majority PAC.
Sen. Tom Cotton, R-Ark., has played a key role in keeping off the table a deal over Deferred Action for Childhood Arrivals, a program that gives protection to dreamers. He was one of many Republicans promising to make the impasse painful for Democrats.
Five days before the vote, Cotton tweeted that a shutdown over the DACA issue would backfire on Democratic senators up for re-election "in places like W.Va., Ind., Mo., N.D., & Mont.," referring to the five states on the 2018 map where Trump won landslides.
"They ignored the needs of millions of Americans who rely on the federal government for important services," Senate Majority Leader Mitch McConnell, R-Ky., said early Friday morning. "They held all this hostage over the completely unrelated issue of illegal immigration."
On Friday, just four of the senators cited by Cotton voted to adopt a Republican funding bill that did not deal with DACA. Tester voted with the majority of Democrats, while new Sen. Doug Jones, D-Ala., who does not face voters until 2020, backed the bill on the grounds that it would extend CHIP.
Less clear was how powerful the backlash might be within the Democratic base. At a closed-door meeting of Democratic senators Friday night before votes, nobody rose to say that the party's strategy put his or her seat at risk, said two people in attendance.
Meanwhile, the liberal Indivisible Project, which was founded by Capitol Hill veterans and boasts thousands of local chapters, has focused its efforts more on holdout Democrats from blue and purple states, such as senators Mark Warner and Tim Kaine of Virginia, both of whom had voted to keep the government open in December - but not this time.
Similarly, United We Dream, a group advocating for dreamers that has organized months of in-person protests in states and on the Hill - including sit-ins at senators' offices - made a subtle shift in January, focusing on reluctant Republicans and thanking Democrats as they came on board.
"The Republicans are trying to isolate us, as part of a white supremacist strategy to isolate people of color," said Greisa Martinez, director of advocacy and policy at United We Dream. "That's not hyperbole - we heard the (vulgar) language that the president used last week."
Meanwhile, Democrats assembled the votes to block the House bill, with their 2018 candidates coming up with multiple reasons to join in. Kaine, whose shutdown-averse state is home to the largest concentration of federal workers in the country, had praised the short-term spending bill in December as a "solution that avoided brinkmanship." But with imminent deals on hurricane relief or DACA, he said, "enough is enough."
Kaine rejected Republicans' characterization that Democrats will own the shutdown, saying his vote merely amps up the pressure to finalize a budget.
The five holdout Democrats - Jones, Joe Donnelly of Indiana, Heidi Heitkamp of North Dakota, Joe Manchin III of West Virginia and Claire McCaskill of Missouri - did earn some enmity from liberal groups. Justice Democrats, founded in 2017 to threaten primary challenges to "corporate Democrats," tweeted photos of the five and promised to "replace them in 2018." After Donnelly announced his yes vote for the GOP bill, Jesse Myerson, an organizer with the liberal Indiana group Hoosier Action, tweeted that "in order to beat the Republicans this year he will need PEOPLE who are ENTHUSIASTIC enough about him to CAMPAIGN for him."
Yet there's little evidence that the holdout Democrats are at risk of primary defeats.
Of the four up for re-election this year, only Manchin has an opponent who has filed a campaign finance report. As of Sept. 30, challenger Paula Jean Swearingen had $59,783 on hand, while Manchin had $4,131,896.
Manchin said at least 9,000 children in West Virginia are on the verge of immediately losing their CHIP coverage, and about 50,000 in his state are covered by the program. "I hear from them and their families all the time. But if you explain and you tell them the argument on DACA, what's happened and what it means, they're very sympathetic."
The groups working most closely with Democrats had few complaints. In December, they had been frustrated, but held at bay, when 18 Democrats voted for a short-term spending bill that did not extend DACA. On Friday, when asked about their colleagues who were likely to hold out, the Senate's liberals said that activists had already succeeded in moving a critical mass of Democrats to their position.
"When we began opposition to these (spending bills), I was one of seven," said Sen. Bernie Sanders, I-Vt., shortly before the vote. "The next time we did it, we had 30. Now we're above 40. I think we're making progress on this issue."