The beginning of the collapse of House Speaker John A. Boehner’s border bill came Wednesday evening, when Texas Sen. Ted Cruz gathered more than a dozen House Republicans at his office in the Dirksen building on Capitol Hill.

It was there, as Boehner (R-Ohio) held his own meetings on the other side of Constitution Avenue, that Cruz heard that the speaker didn’t have enough votes — and realized that if his House allies held firm, he could rupture the fragile coalition supporting the measure.

Around the room — amid the boxes of pizza and cans of Dr Pepper, a Texas favorite — were longtime Cruz confidants, such as Rep. Michele Bachmann (Minn.), and more recent ones, such as Reps. Todd Rokita (Ind.) and Marsha Blackburn (Tenn.).

For more than an hour, the 13 House members complained, often bitterly, about Boehner’s bill, several attendees said. The speaker, with his $659 million measure that would fund federal agencies and bolster security along the U.S.-Mexico border, was ignoring the real issue, they said.

The problem, they said, was President Obama’s Deferred Action for Child Arrivals program, the product of a 2012 executive order that granted temporary relief for some children of illegal immigrants. They wanted it gone, gutted, and they were furious that Boehner wouldn’t touch it.

Careful not to be viewed as orchestrating action in the House, even though he holds regular “fellowship” meetings with members, Cruz listened quietly and nodded along as his guests laid out their concerns and discussed possible demands for Boehner.

He agreed that Boehner was distracted and said they should stick to their principles. The freshman senator also reminded them to be skeptical of promises from House leaders, particularly of “show votes” — legislative action designed to placate conservatives that carry little, if any, weight.

That quiet assurance was enough to persuade the conservatives to effectively topple Boehner’s plan, at least on Thursday, by balking when he said he would hold a largely symbolic standalone vote on Obama’s program.

Bachmann told reporters in a gaggle Thursday morning that she would not “vote for a bill that is going to look good but do nothing.” Rep. Louie Gohmert (R-Tex.), who also attended the Cruz session, scowled when asked whether he would back Boehner, and said, “I’m not there yet.”

In an interview, Cruz said that he did not dictate what the members should do, but only reaffirmed his position against Boehner’s plan.

“The suggestion by some that House members are unable to stand up and fight for their own conservative principles is offensive and belittling to House conservatives,” Cruz said. “They know what they believe and it would be absurd for anyone to try to tell them what to think.”

A first-term senator wielding such influence in the House is both unusual and a testament to the ongoing tumult within the Republican Party. Sensing a desire by many in the House to follow an unyielding conservative, Cruz has gladly taken on that role, bolstering his national profile ahead of a potential 2016 presidential campaign.

More than 57,000 unaccompanied minors have crossed into the United States from Mexico since October 2013. Here are 10 numbers to know about the growing humanitarian crisis. (Tom LeGro and Natalie Jennings/The Washington Post)

Cruz’s tight embrace of House conservatives also has given him a powerful network inside and outside of Congress, even as he has been marginalized by Democrats and many of his fellow Republicans in the Senate. Ignoring them, Cruz has turned friendly news media outlets, conservative advocacy groups and House backbenchers into his base.

Rep. Steve King (R-Iowa) called him a “perfect catalyst” who has a “real rapport with conservatives in the House.”

Not so much with leaders of the House. When asked what they thought of Cruz’s meddling, Boehner associates were livid as usual — off the record — but timid about it. Ever since last year’s federal government shutdown, when Cruz broke with Boehner and became a hero to grass-roots activists, there has been intensifying ire toward Cruz but a general reluctance to challenge the right’s new star.

When asked for a comment about Cruz’s role on the border bill, Boehner’s office declined.

Cruz did sustain some criticism from fellow Republicans.

“I think Senator Cruz is exercising his right as a senator to take positions that he thinks are the proper ones,” said Rep. Joe Barton (R-Tex.). “I do think it would be helpful if he could pass those positions in the Senate before he asked the House to reciprocate or to act first. I think his general strategy is appropriate and acceptable, I think sometimes the tactical situation is different in the House and I’m not sure he takes that into mind.”

Democrats have seized on Cruz’s ascent within the GOP and used his growing sway to depict him as the true leader of an unruly House Republican caucus. Shortly after the border bill was pulled Thursday, American Bridge, a Democratic super PAC, issued a statement saying, “Speaker Cruz has the House back on Cruz control,” complete with a picture of Cruz pushing Boehner in a toy car, as a parent would a child.

Rep. Jim Himes (D-Conn.) issued a taunting poem via Twitter: “Sittin’ at my desk, watchin’ the news, rest of the day is up to Ted Cruz.” Rep. Mark Pocan (D-Wis.), also via Twitter, asked Cruz about the floor schedule: “Just thought I’d go right to the source, will the House be voting tonight?”

The House did not vote Thursday, choosing instead to give it another go on Friday after a morning conference meeting.

The Wednesday night dinner was far from the first between Cruz and like-minded House members. Over pizza, breakfasts and phone calls this month, Cruz encouraged many of them to oppose Boehner, out-whipping the leader of the House.

Last week, Cruz attended a breakfast with House conservatives held by King, a critic of comprehensive immigration reform. King and his aides served Chick-fil-A breakfast items and coffee at the meeting, which was held in a conference room at the Capitol.

“He really wanted to hear from people in the room,” King said. “He also let us know that anything we send to the Senate, if it comes back, it’s going to be terrible, so we should make sure we’re ready to respond to that.”

Cruz defended his meetings as efforts to work more closely with conservatives, not forums to work against Boehner.

“One of the unfortunate things in Washington is how little communication there is between members of House and Senate,” Cruz said in the interview. “For many months, I’ve been periodically hosting gatherings with House members to discuss issues and challenges of the day and our gathering last night was scheduled several weeks ago.”

The idea that the freshman is looking to be speaker in all but name is “hyperbole,” Cruz added, uttered by “Democrats desperate to shift blame.”

“In the months before an election, or heading into a congressional recess, we always seem to enter silly season,” he said. “The focus of this debate needs to remain on the cause of the crisis and the cause of the crisis is President Obama’s refusal to follow the law.”

Ed O’Keefe contributed to this report.