The United States Congress took six months to approve a supplemental spending bill that includes aid to Ukraine, Israel, and Taiwan. The drama, legislative maneuvering, and threats to remove a second speaker of the House of Representatives have left reasonable people asking what, exactly, is going on with Republican legislators: Have they recognized the perilous state of the world and the importance of U.S. leadership? Or was the difficulty in securing the aid the real signal worth paying attention to—making Republican support for the assistance just a last gasp of a conservative internationalism that is no longer a going concern?In the breach between these two narratives lies the future of the Republican Party—whether it has become wholly beholden to the America First proclivities of Donald Trump or can be wrenched back to the reliably internationalist foreign policy of Dwight Eisenhower and Ronald Reagan.Former President Trump has long questioned the value to the U.S. of international alliances, trade, and treaties, and involvement in global institutions. Senator J. D. Vance of Ohio, who propounds the Trumpian view, recently said of the fight over the supplemental spending bill: “Notwithstanding some lingering Cold Warriors, we’re winning the debate because reality is on our side.” And Vance may be right about who’s winning: 22 of the 49 Republicans in the Senate voted for the supplemental when it was presented in February, at a time when Trump was agitating against it; Speaker of the House Mike Johnson persuaded Trump to stay on the sidelines for the April vote, and five more Republican senators opposed the legislation anyway. That suggests a rising, not ebbing, tide.If Vance is correct, this could be the last aid package for Ukraine—meaning that Ukraine will ultimately lose its war with Russia. Republicans will have the U.S. pull away from alliance commitments in Asia and Europe and withdraw from participating in trade agreements and international institutions.[Anne Applebaum: The GOP’s Pro-Russia caucus lost. Now Ukraine has to win.]But Republican lawmakers and voters are far from united around this worldview. Despite the onslaught against internationalism, Republican voter support for NATO has decreased only marginally, from 44 percent in 2015 to 43 percent currently. And despite some radical party members’ fulminating that Republicans who’d voted for the supplemental would be hounded by voters, no backlash actually took place.Some Republican legislators who supported the supplemental spoke of it in terms redolent of the internationalist Republican tradition. House Appropriations Chair Tom Cole, of Oklahoma, said: “This House just showed tyrants and despots who wish harm upon us and our allies that we will not waver as the beacon of leadership and liberty.” Johnson, who’d formerly voted against aid to Ukraine, put his job on the line to get the bill passed, in the name of doing what he said was “the right thing.” Representative Mike McCaul of Texas, chairman of the Foreign Affairs Committee, described the speaker’s reversal as “transformational … he’s realizing that the world depends on this.” And if that is indeed where Johnson stands, he does so in the company of Senate Minority Leader Mitch McConnell, who has indicated that he will commit his final two years in the Senate to restoring Republican internationalism.Ultimately, the Republican Party’s direction will become clear based on the policies it chooses to oppose or support. The supplemental was one test; some of the others are less high-profile but at least as consequential, if not more so, because they concern the very building blocks of a conservative international order. Given that the leader of the Republican Party does not favor these ideas, creating policies to advance them will be difficult. But difficult is not impossible, as the success of the supplemental shows.For example: Will Republicans fight to increase defense spending? The past four presidential administrations have failed to spend even what was needed to carry out their own national-security strategies—and this at a time when the world has been growing more dangerous, as U.S. adversaries have coalesced into an axis of authoritarian powers. Defense spending is popular with the public: In a Reagan Institute poll, 77 percent of Americans said that they favored bumping it up. But doing so will require a reordering of priorities, whether through reforming entitlements, raising taxes, shifting money from domestic to defense budgets, adopting policies that speed economic growth, or allowing deficits to continue to balloon. Republican willingness to make these hard choices in order to spend more on defense—particularly on ship building and munitions stocks—will be a leading indicator as to whether the internationalists among them are gaining ground.So, too, will the Republican stance toward the United Nations Convention on the Law of the Sea, which establishes rules for navigation and boundaries for the exploitation of maritime resources. The convention commits countries to recognizing that territorial waters become international 12 nautical miles from shorelines, and it delineates countries’ exclusive national zones for mining and fishing. In 1994, the United States signed the convention, which has also been signed by 168 other nations and the European Union. But the U.S. Senate has so far refused to ratify it. Conservatives are concerned that the convention impinges on U.S. sovereignty; even the urging of former President George W. Bush, when he was in office, failed to convince them otherwise.The UN Convention on the Law of the Sea sets terms that the United States already abides by and enforces on other countries. Without it, America may be forced to comply with the rules its adversaries—chiefly Russia and China—prefer to establish, or else to spend time and money protecting itself and its allies against those countries’ maritime activities. Every living chief of naval operations advocates the convention’s passage. And countries contending with Chinese claims in the South China Sea view U.S. ratification as an indicator of American commitment to the rules-based order on which they rely. Republican Senator Lisa Murkowski and Democrats Mazie Hirono and Tim Kaine have introduced a resolution to ratify the convention. Republicans will have to decide whether they will provide the votes to pass it or make hostility to treaties a hallmark of their party.[George Packer: ‘We only need some metal things’]Similarly, the GOP will need to decide exactly what its posture will be on international free trade. Efforts to integrate China into the global economic order on equal terms failed; as a result, both American parties lost their appetite for international trade agreements and turned instead to imposing punitive tariffs on China and restricting its market access. This approach has not been successful either. In fact, the bipartisan retreat from global trade agreements as a lever of international power comes at a time when more Americans—eight in 10—view international trade as beneficial to consumers such as themselves than at any other time in the past 50 years. My American Enterprise Institute colleagues Dan Blumenthal and Derek Scissors have argued for updating trade agreements in the Western Hemisphere—as the Trump administration did with the North American Free Trade Agreement—while prioritizing new agreements with Japan, Taiwan, the Philippines, and Indonesia. A truly internationalist Republican Party will pursue such a policy, which would strengthen the trade links among Western nations.In recent years, the United States has withdrawn from dominant roles in numerous international institutions. Neither the Trump administration nor the Biden administration bothered to nominate judges for the World Trade Organization, greatly weakening that body. Meanwhile, China secured leadership roles in Interpol and in the UN agencies that regulate international telecommunications, air routes, and agricultural and industrial assistance. China nearly assumed leadership of the UN’s international maritime organization, which would have allowed it to rewrite the rules for freedom of navigation. Perhaps Republicans can be persuaded that ceding such positions to China is damaging. Much as with the Convention on the Law of the Sea, Washington and its allies can either lead the institutions that set and enforce rules or work to shield their interests from the reach of them. Setting the rules is more cost-effective.How the Republican Party addresses these nuts-and-bolts national-security policies will reveal its true direction—whether it will continue to lurch toward Senator Vance’s America First policies or return to the values it came to embody after World War II. Even if Donald Trump—the avatar and motive force behind America First—returns to the presidency, Speaker Johnson’s adroit management of the supplemental bill shows that Congress is not powerless. By reasserting its constitutional prerogatives, the legislature can constrain the executive. But for that to happen on national security, Republicans have to believe that American security and prosperity require active engagement in the world.