(Photo: AP)

Congressional Democrats have convulsed into their deepest and most bitter rifts since taking House control in January, and it took a motherhood and apple pie issue like improving horrific conditions for children and other migrants seized crossing the southwest border to do it.

Lawmakers overwhelmingly sent President Donald Trump a $4.6 billion package on Thursday that bolsters care for the tens of thousands of arrivals taken into custody monthly and imposes guidelines on how the Trump administration must handle them. But the measure dealt a blow to House Speaker Nancy Pelosi , D-Calif., who was forced to accept weaker legislation than she and many liberals wanted, and it generated shockwaves across her party.

It pitted House and Senate Democrats against each other and highlighted discord between the House’s sizable progressive and centrist factions. It showed that Pelosi faces a challenging balancing act that goes well beyond coping with a handful of vocal, liberal freshmen like Rep. Alexandria Ocasio-Cortez, D-NY.

The fight suggested that similar power plays between the liberal and moderate blocs could arise, complicating Democrats’ efforts to address marquee issues like health care and climate change . And it echoed problems faced by recent Republican speakers when they controlled the House and saw priorities derailed by members of the GOP’s hard-right, often unyielding House Freedom Caucus.

“It is not good for our unity,” said Rep. Pramila Jayapal, D-Wash., a liberal leader, adding, “This is a very rough patch.”

While both chambers of Congress approved the package by lopsided margins, Senate Democrats led by Minority Leader Chuck Schumer backed it overwhelmingly, with just six Democrats voting “no.” They argued they’d cut the best deal they could in the Republican-controlled chamber, where the rules virtually force the two parties to compromise if legislation is to pass.

“You’ve got a 30-1 vote,” said Sen. Patrick Leahy, D-Vt., Senate Democrats’ chief negotiator on the measure, citing the Appropriations Committee’s overwhelming approval, which presaged the Senate’s 84-8 final passage. “Around here these days you couldn’t get 30-1 that the sun rises in the East.”

Yet when the House voted 305-102 to send the measure to Trump, Pelosi’s Democrats split 129-95 for the measure. Even many who backed it did so grudgingly, reflecting the pull between helping children who have been stockaded in overcrowded, squalid facilities and a deep distrust of how Trump will actually use the funds. House Democrats accused their Senate counterparts of killing their leverage to strengthen the measure by backing the legislation so strongly, and even the usually measured Pelosi couldn’t resist a dig.

“We will not engage in the same disrespectful behavior that the Senate did in ignoring the House priorities,” she said. “In order to get resources to the children fastest, we will reluctantly put the Senate bill on the floor.”

House Democrats were riven internally, with moderates saying liberals were living in a dream world if they thought they could force Republicans to alter the bill.

Veteran Rep. John Yarmuth, D-Ky., said the outcome had long been obvious, comparing it to Western movies with a predictable outcome. “But there were some in our caucus who didn’t like the ending that was inevitable,” he said.

Countered Rep. Raul Grijalva, D-Ariz., a top liberal, “Our efforts to try to make this bill much more humane than it is now were basically thrown under the bus” by moderates.

Progressives wanted to buttress the measure with provisions preventing Trump from transferring money to toughening border security or buying more beds so authorities could detain more migrants. They also sought language strengthening requirements for how migrants are cared for and making it easier for members of Congress to make snap visits to holding facilities.

But swing district moderates, worried they’d be accused of weakening immigration law enforcement and needlessly delaying the aid, warned early Thursday that they would oppose adding such provisions to the bill.

It was already clear that any House changes would die in the Senate, where overpowering bipartisan support for the Senate bill made it what Senate Majority Leader Mitch McConnell, R-Ky., called “the only game in town.” Holding almost no cards, Pelosi abruptly brought the Senate-approved bill to the House floor, without the revisions, infuriating progressives.

“I honestly think they do not understand, or they are callous to, the needs of holding the administration accountable,” said Jayapal, expressing her rage at Senate Democrats.

Spotlighting Democrats’ internal turmoil, 24 members of the Congressional Hispanic Caucus voted against the measure and only eight supported it. The group, for whom immigration and improving the treatment of migrants are top priorities, called the bill “a betrayal of our American values” in a statement.

“We have a president who is very untrustworthy, and giving him a blank check is very frightening for me,” said Rep. Veronica Escobar, D-Texas, who opposed the measure. In an indication that the fight could have personal repercussions among Democrats, Escobar said of moderates, “I wish even one of them had spoken to me.”

When it was over, moderates reveled in the clout they’d wielded over the more highly publicized progressive wing of the party and said the day had delivered a message to leaders about issues lying ahead.

Rep. Jeff Van Drew, D-NJ, said of his fellow centrists, “their votes are needed and their thoughts are needed.”