The pre-eminence of the legislative branch is perhaps the most distinctive feature of American democracy. If the Constitution was designed to be a firewall against despotism, then Article I, which defines the powers of the Senate and the House of Representatives, is its keystone, keeping decisions over spending, taxation, and other major policies close to the people and out of the hands of any single ruler.

On matters of foreign policy, however, the picture is famously mixed, with the legislative and executive branches left to struggle over constitutional powers that are shared or left undefined. In practice, the executive branch has often prevailed in this struggle: "The direction of war," Alexander Hamilton declared, demands "the exercise of power by a single hand." The same has historically been true of the projection of America's diplomatic and economic power.

And yet, at critical moments throughout our nation's history, Congress has asserted itself as an essential check on the President's foreign policy powers. Senate hearings on the Vietnam War played a decisive role in turning public opinion against the conflict and accelerating the US troop withdrawal. During Ronald Reagan's administration, Congress uncovered and reversed the President's policy of covert support for anti-leftist militias in Central America, and delivered a bipartisan rebuke of his policy toward apartheid South Africa.

At various junctures, Congress has led the way in reorganizing the Pentagon, achieving nuclear threat reduction in the former Soviet Union, and reforming the intelligence community.

We believe that our country's situation today requires such leadership -- not merely an assertion of congressional powers, but an assumption of new responsibilities.

In the first 10 months of his administration, President Donald Trump has, among other actions: questioned the principle of mutual self-defense that has formed the bedrock of our NATO alliance for six decades; withdrawn the United States from the most significant global climate agreement in history, which every other country in the world has now signed or ratified; provoked a destabilizing war of words with nuclear-armed North Korea while sowing doubts about America's commitment to our allies in East Asia; submitted a budget proposal to Congress that would drastically cut diplomatic personnel, foreign assistance, and contributions to international organizations; and disparaged and marginalized the work of career diplomats and foreign policy experts, asserting that "I am the only one that matters" when it comes to America's international relations.

Each of these actions flies in the face of the popular -- and bipartisan -- consensus regarding America's role in the world that has guided our foreign policy since the end of the Second World War. Far from making America great again, they have unsettled our allies, encouraged our adversaries, and undermined our moral authority.

These trends are not immutable, but reversing them will require Congress, on a bipartisan basis, to flex its constitutional muscle. We have already seen some promising, if tentative, signs of such assertiveness.

The House and Senate rejected President Trump's foreign affairs budget nearly in its entirety -- though funding diplomacy and development at minimally adequate levels will still require a bipartisan budget agreement before the end of the year.

Congress voted nearly unanimously to remove the President's discretion to grant sanctions relief to Russia, despite objections from the administration. And Congress has quietly begun to pursue greater congressional oversight over the President's use of force, for example by revisiting the Authorization for the Use of Military Force used by the last three presidents to justify counterterrorism operations abroad.

These are steps in the right direction, but they are only a start. If America's role as a global economic leader, a guarantor of security for our allies and a defender of human rights and democracy is to survive, Congress must do more.

Funding bills, for example, will need to be more carefully crafted to safeguard key priorities and provide leverage against authoritarian abuses. Hearings will need to be stepped up to scrutinize executive actions, more carefully vet personnel, and examine congressional options in response.

Members of Congress are already finding themselves cast in a new role as interpreters of foreign policy and affirmers of basic American values and commitments. As they travel abroad and engage in interparliamentary exchanges, there is every reason to amplify this role.

Congress must also stop the hollowing out of our diplomatic capacity. It can do this through the appropriations process and stepped-up oversight, consultation and scrutiny of nominees. The Trump administration has failed to fill key diplomatic positions and has appointed unqualified loyalists to the few senior positions that have been filled.

It has marginalized experts and deployed senior officials to perform clerical tasks. It has shown a preference for off-the-cuff remarks over diplomatic protocols. As a growing number of senior diplomats have warned, this all-consuming push to "reform" the State Department is doing untold damage that will take years, if not generations, to reverse.

We offer two caveats in conclusion. First, we understand very well the current dysfunctions and failings of Congress. The institution can barely keep the government's lights on, much less address critical national priorities such as immigration and infrastructure. But Congress is still a democratic bastion and the best recourse we have.

Second, we are not claiming that legislative assertiveness in foreign policy is an ideal or complete solution. There are many areas where Congress will never totally substitute for the executive branch, including the persistent and painstaking work of diplomacy.

But with the President consistently falling short of the mature judgment and discerning decision-making required of the leader of the free world, Congress has no choice but to respond and compensate. That is what our constitutional framers intended. America's role in the world depends on it. It is an Article I moment, and Congress must measure up.