Timothy Kaine

Despite serving in the minority, Kaine, a former missionary in Honduras known for his affable demeanor, has repeatedly managed to force the Senate into hours of debate and five votes aimed at limiting Trump’s ability to wield military power without lawmakers’ approval. The latest was a resolution that would have immediately halted the war in Iran and required the president to seek authorization to continue Operation Epic Fury, the name of the campaign.

The measure failed, as did a similar one Kaine led last June regarding a more limited military operation against Iran. But his efforts have forced senators -- including Republicans who have previously espoused the “America First” slogan on which Trump ran for office, promising to end wars rather than start them -- to go on the record with votes declaring where they stood. The same has been true for resolutions governing the use of force in Venezuela and for one in the coming days barring military intervention in Cuba without congressional approval.

Polls show that a majority of Americans oppose the military action in Iran. But Kaine said the resolutions are less about politics than about his desire to get back to the separation of powers outlined in the Constitution, after decades of Congress abdicating its role in questions of war.

“I’m a real purist about this,” Kaine said in an interview. “I tell people that I came to the Senate with 100 interests and passions, and one obsession. And this is my obsession -- getting this decision correct.”

While the Constitution grants Congress the power to declare war -- something it has not done since World War II -- it also gives the president authority to act in defense of the nation. Over the last several decades, Congress has approved authorizations for the use of military force, which confer the executive with powers to direct military action without an immediate need to consult with the legislative branch.

“The reason the Constitution matters here -- it’s not just a procedural thing,” Kaine said. “We’re risking our kids’ lives.”

To force the issue, Kaine has relied on a 1973 law known as the War Powers Resolution, which allows any senator to go around the normal legislative process controlled by the majority and force quick consideration of a measure to withdraw US forces abroad, in the absence of congressional authorization.

Kaine has deployed the tactic five times since early last year to challenge Trump’s use of offensive military force.

When he first arrived on Capitol Hill, Kaine asked for special permission to serve on the Foreign Relations and Armed Services committees, two high-profile and sought-after panels. He said that he thought it would give him “the opportunity to try to take an issue that nobody seemed to care about then and make more people care about it.”

In the years since, he has used his perch to press administrations of both parties to respect Congress’s power to declare war. He prides himself on what he said was having applied a uniform standard to Trump, Barack Obama and Joe Biden.

“I’ve tried to be consistent about that,” he said.

During the Obama administration, Kaine, the father of a Marine reservist, urged the White House to seek authorization as the US expanded military campaigns across the Middle East.

He criticized Trump’s decision during his first term to authorize the strike that killed General Qassem Soleimani, who was Iran’s top security and intelligence commander.

And he supported a failed congressional effort that would have forced Biden to withdraw troops from Niger.

But the results have also been uniformly disappointing, as successive Congresses have failed to claw back their prerogatives and as presidents of both parties have taken the position that they are not bound by the legislative branch when it comes to military operations.

“I can’t say that I’ve made the progress that I wish I had,” Kaine said.

His zeal for the issue is rooted in his state’s deep military ties. Virginia is home to more than 100,000 active-duty and reserve military personnel, the Pentagon, and the largest naval base in the world, in Norfolk.

Some of his work has drawn bipartisan backing. He has partnered with Senator Rand Paul, a Kentucky Republican, on a number of war powers resolutions. And with Republican Senator Todd Young of Indiana, he helped pass a repeal of a decades-old congressional authorization for use of military force from the Iraq War era that critics said had been stretched far beyond its original purpose.

At times, his resolutions challenging the administration have attracted wider support from Republicans. A January vote days after the capture of President Nicolás Maduro of Venezuela initially drew support from five Republicans but failed after the White House pressed those lawmakers to switch their position and help kill it.

Kaine sees a silver lining in the failures.

“I came into the Senate looking at legislation just the way most people do: It’s either going to pass, or it’s going to fail,” he said, but he had come to realize you actually can change behavior.

He pointed to Venezuela as an example. After his measure drew some unexpected Republican backing, the White House moved quickly to reassure lawmakers that the operation would not involve deploying US troops in the country without congressional authorization.

Officials also agreed to the first public hearing examining the campaign targeting vessels in the Caribbean and the broader strategy with Venezuela following the capture of its leader.

Republicans, however, have accused him of using the measures to score political points rather than pursue serious oversight.

“This isn’t about advancing the needs of the nation,” Senator John Barrasso of Wyoming, the No. 2 Republican, said of the Iran resolution. “It isn’t about helping people. It’s not about protecting Americans. None of that is true.”

He added, “It’s about slowing down the Senate, throwing instruments into the gears, all to try to create theater.”

Others who say they share Kaine’s constitutional concerns have questioned whether the series of votes he has forced are really addressing the issue.

Kaine is not letting up, and other Democrats are using the same tactics. Last week, five additional war powers resolutions were introduced in the Senate -- all co-sponsored by Kaine.

Some Democrats say the repeated votes are intended to keep pressure on the administration and their colleagues as the conflict wears on and casualties mount. Others see the threat of consuming more Senate floor time as leverage to demand public hearings from the Trump administration to explain its objectives and strategy in Iran.

So far, lawmakers have received a series of classified briefings on the conflict, but no public hearings have been scheduled. Democrats are also pressing for an investigation into the bombing of an Iranian school that killed scores of children, an episode that has fueled criticism of the military campaign.