Donald Trump’s military strike in Syria on Thursday won cautious bipartisan approval on Capitol Hill.

Leaders of both parties reacted positively to what they saw as “a proportional response to the regime’s use of chemical weapons”, in the words of the House minority leader, Nancy Pelosi. However, Democrats and some Republicans argued for the necessity of congressional action to justify future military action against the Assad regime.

The decision to launch five dozen Tomahawk missiles against an Assad regime airfield scrambled partisan lines. Debate on intervention in the Middle East has not often cleanly followed political ideology in recent years, and Trump himself ran as a non-interventionist candidate in the region. In contrast, his Democratic opponent, Hillary Clinton, had long struck a more hawkish tone against Bashar al-Assad and called for strikes against his regime as recently as Thursday afternoon.

The key dividing line between Democrats and Republicans was the necessity for immediate congressional action. Top Republicans often praised the strike without mentioning any role for the legislative branch. Republican Marco Rubio of Florida simply praised Trump in a statement for “ma[king] it clear to Assad and those who empower him that the days of committing war crimes with impunity are over”.

Rubio, who bitterly clashed with Trump over foreign policy during the 2016 presidential campaign, said he was “heartened” to see the president “was deeply impacted” by the attack. “I believe he really was, and I think it will go down as a key moment in his presidency,” Rubio, who sits on the Senate intelligence committee, told the Guardian.

“I think we’ll look back on that moment tragically, because of what happened, but as a moment where they really understood who we’re dealing with here.”

While Rubio voiced his approval for the initial action against Assad’s regime, he noted the US response had to be one that “permanently undermines and deteriorates the ability of Assad to continue to conduct these sorts of chemical attacks against innocent civilians”.

In contrast, Ben Cardin of Maryland, the top Democrat on the Senate foreign relations committee, struck a slightly different tone. Although Cardin believed “military strikes against Assad’s arsenal send a clear signal that the US will stand up for internationally accepted norms and rules against the use of chemical weapons”, he made clear that Congress needed to be involved in the future.

“However, and I cannot emphasize this enough, any longer-term or larger military operation in Syria by the Trump administration will need to be done in consultation with the Congress,” said Cardin. The Maryland Democrat added: “Furthermore, it is the president’s responsibility to inform the legislative branch and the American people about his larger policy in Syria, as well as the legal basis for this action and any additional military activities in that country”.

Cardin’s Republican counterpart on the Senate foreign relations committee echoed his belief on the need for congressional actions.

“I would hope that [Trump] would come to Congress,” Bob Corker told reporters on Thursday night. “It depends on what’s being proposed.”

Corker said he believed the chemical weapons attack proved “a very clarifying moment for the president” with respect to Assad. It was equally important, he added, for the administration to understand the motivations of the Russian president, Vladimir Putin.

“We need to put tremendous pressure on Putin,” Corker said.

Some on Capitol Hill were far less supportive. Among libertarians within the GOP, Senator Rand Paul quickly issued a statement expressing his skepticism. “While we all condemn the atrocities in Syria, the United States was not attacked,” said the Kentucky senator. “Our prior interventions in this region have done nothing to make us safer and Syria will be no different.”

Tulsi Gabbard of Hawaii, a Democrat who met with Assad in January and suggested on Twitter that the Assad regime was not actually responsible for the chemical weapons attack on civilians that prompted the missle strike, also opposed Trump’s actions. “It angers and saddens me that President Trump has taken the advice of war hawks and escalated our illegal regime change war to overthrow the Syrian government,” said Gabbard in a statement.

This strong opposition to the strikes was shared by members of an ideological fringe that has long fervently supported Trump. Leaders of the so-called “alt-right” expressed shock and anger at the president’s decision, and some on the racist far-right pledged to campaign against war.

Richard Spencer, whose post-election shout of “Hail Trump!” was greeted with Nazi salutes, called Trump’s decision to strike in Syria a “betrayal”.

In a public video posted late Thursday night, Spencer said he was shocked, disappointed, and “ready to condemn Donald Trump”.

Spencer also shared a photo and tweeted that he wanted to “stand with Assad”.