But now some are up in arms about the Trump administration's recent missile strikes against Syria. Given that there is no clear threat to the national interest, they argue that Trump needs to request authority from Congress to undertake this mission. Several Democrats have insisted that if the president doesn't seek permission, then he is exceeding his constitutional power.
Rep. Eliot Engel of New York, the highest-ranking Democrat on the House Foreign Affairs Committee, praised the missile strikes in Syria as an appropriate response to the regime's use of chemical weapons. But he also said
that "military force against Assad can only continue in the long term with congressional approval." Virginia Democrat and former vice presidential candidate Sen. Tim Kaine called the strike in Syria "unlawful"
since Trump had not obtained approval from Congress.
But presidents from both parties have made a series of decisions that gradually weakened the role of Congress in shaping national security decisions while granting the White House much greater leeway to decide when and how to use America's military power.
The first thing to go was the declaration of war. Starting with President Harry Truman's actions in Korea, commanders in chief have deployed troops overseas without requesting a formal declaration of war from Congress, as FDR had done in 1941. Presidents have requested ceremonial resolutions of support for using military force from Congress, as President Lyndon Johnson did in August 1964 with the Gulf of Tonkin Resolution, but then proceeded to shape and expand military operations without really involving the legislative branch.
Even after the passage of the War Powers Resolution in 1973, which was meant to reassert congressional war-making power, presidents have continued to act with a relatively free hand. Although President Obama was more sensitive than most to the impact of this approach, he didn't do much to move away from the wartime framework used to fight terrorism.
Obama followed the plan adopted by President George W. Bush after 9/11 when Congress granted the president to "use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001." That authorization has been used to justify drone strikes.
The executive branch itself has become massive since the Cold War, with institutions such as the CIA and the National Security Agency having tremendous authority to conduct secret operations and surveillance against foes overseas as well as potential threats at home. There have been moments, such as the mid-1970s with the Sen. Frank Church hearings
into wrongdoing by the CIA, when Congress pushed back by implementing reforms that curbed the power of these organizations. But such moves have been limited.
As the nation discovered with the Edward Snowden leaks about surveillance, Congress has generally allowed the national security state to operate with a relatively free hand in the name of protecting the homeland.
When presidents have used air power and special operations forces in response to perceived specific threats abroad, congressional pushback has been rare.
There have only been a few exceptions, such in 2013 when Republicans in Congress would not support President Obama when he wanted to attack Syria in response for its regime using chemical weapons. By contrast, neither party complained much when Obama conducted an aggressive drone campaign against terrorists.
Some members of Congress have publicly criticized the White House or threatened to use the power of the purse to limit use of the military. But rarely have they done much to actually prevent presidents from taking those kinds of steps.
The fact that Democrats in Congress have joined Republicans in this embrace of executive power does not mean the legislative branch does not have immense authority.
Congress retains power over military spending, Congress has the ability to investigate presidential misconduct and Congress has the ability to conduct aggressive oversight on executive agencies. In addition, members of Congress have the power to command media attention and cause problems for presidents as they undertake these missions.
When enough legislators opposed the war in Vietnam, they were able to bring massive pressure against President Nixon to finally draw down the war. But too often both parties have failed to use those powers.
When Democrats blast Trump, it's hard for many Americans -- including liberals who have a genuine problem with what the President is doing -- to take them seriously. Both parties have been participants in vastly expanding executive power on national security and complicit in standing by as this occurred.
To be sure, there have been some critics. A small group of Democrats unsuccessfully sued President George H.W. Bush when he sent troops to oust the Iraqis after the invasion of Kuwait.
Politicians in both parties have created a presidency with immense authority to use military force without any substantive checks on power. So if Democrats feel that President Trump has too much freedom to use force as he sees fit, they might want to take a look in the mirror and evaluate some of the historical decisions they themselves have made.