WASHINGTON ― Sen. Bernie Sanders (I-Vt.) will use a major foreign policy address Thursday to set out his view of how politicians on the left should discuss the U.S role in the world and why voters at home should pay close attention to America’s actions abroad.

Even as the popular lawmaker built a national reputation and attracted millions of fans during his unsuccessful candidacy for the Democratic presidential nomination last year, he frequently faced criticism for talking too little about how he would tackle global affairs as president. Now seen as a leader among liberals and a strong 2020 candidate, Sanders is poised to show that he can be a leader in the foreign policy conversation as well.

“He wants to start this debate, in some ways similar to Medicare-for-all, in which he really wanted to broaden the debate on what is possible... and say, here’s some basic progressive values that should guide our thinking about foreign policy,” an aide told HuffPost on Wednesday, referencing Sanders’s move earlier this month to propose expanding Medicare. The senator will focus on the value of international cooperation and less U.S. reliance on hard military power to pursue its goals around the world, rather than going into specific policy recommendations for hot spots like Syria, North Korea and elsewhere.

Developments in the health care policy world have demonstrated the power Sanders and his progressive movement now have over the Democratic Party. Sanders’s idea of government-provided health insurance for all Americans was viewed as a pipe dream even by the Democrats’ last presidential nominee, Hillary Clinton, and he received no support from his colleagues when he introduced a similar bill in 2013. This year, he already has more than a third of the Senate Democratic caucus on board.

Sanders will deliver his speech at noon eastern time at Westminster College in Fulton, Missouri. The location is laden with symbolism. Westminster hosted Winston Churchill not long after the Allies won the Second World War. It’s there that, in 1946, the British-American icon delivered the epoch-defining “Iron Curtain Speech,” the origin of the concept of the Soviet Union trapping much of Europe behind an Iron Curtain and the idea of the “special relationship” between the U.S. and the United Kingdom.

Sanders has acknowledged the strengths of the post-war international order that Churchill and others developed. But he’s also spent years publicly warning that America’s leadership of that order has inspired excessive military adventurism in Washington ― and helped create the conditions, economic and otherwise, that turned Americans toward a man who sees little value in the current order, President Donald Trump.

Sanders will focus on contemporary history to explain what he recommends in foreign policy, the aide said.

“There are two things he’s going to compare and contrast: the Iraq War, which most now agree was a disaster, and the Iran agreement, which is an example of how American leadership should work, where we used diplomacy and mobilized international consensus to address a shared challenge,” the aide continued.

The focus on the deal with Iran, by which that country receives sanctions relief in exchange for providing transparency about its nuclear program, is especially salient, given its strong association with the Obama administration that brokered it and Trump’s apparent determination to sabotage the agreement. It helps tie Sanders to former President Barack Obama, and separate him from Trump. In so doing, it combats charges from political observers who say the senator has not done enough to attach himself to the legacy of the former commander-in-chief, and attempts by some in Trump’s orbit to suggest that the Sanders movement should recognize that the president, with his claims of reining in U.S. ambition abroad, might offer what they’re looking for.

Sanders will highlight why he believes his approach best serves Americans ― not by offering them promises of amorphous U.S. influence, but by directly addressing their daily needs.

“In the same way as in his campaign and in his whole political career, he’s been trying to involve people more in politics, he’ll be making it clear that these are issues that impact your daily life... things like sending troops abroad and the money we wasted in Iraq that could have gone to infrastructure or to healthcare or even to effective foreign aid,” the aide said.

Foreign policy watchers on the left say the time is ripe for a change in the conversation ― particularly given frustration among some progressives about how Obama and Clinton adopted relatively traditional establishment foreign policy positions.

“We haven’t seen much from Democrats on this topic since the election… Sanders has a pretty open field, which has not been normal in the left and center-left space in recent years,” said Heather Hurlburt, an analyst at the New America Foundation and senior U.S. official under President Bill Clinton. “This isn’t an area that anybody of the others who are talked about as possible presidential contenders has rushed out to define.”

A Clinton supporter, Hurlburt said less centrist elements of the Democratic Party have yet to successfully coalesce around a shared vision of U.S. foreign policy. They have expressed opposition to major trade deals, for instance, marking themselves as different from Obama and Clinton, but are only starting to have conversations about how to improve international trade architecture, she said, rather than pursue the path supported by the similarly anti-trade Trump movement, with its more xenophobic and mercantilist undertones.

Phyllis Bennis, a well-known anti-war activist at the Institute for Policy Studies, said she gave Sanders some leeway for not focusing heavily on foreign policy during his run for the Democratic nomination because he saw exposing and addressing U.S. inequality as his most important task.

But she told HuffPost she was disappointed by some of his choices when he did take on the subject: He was brave to not attend the American Israel Public Affairs Committee conference in 2016, she said, and instead deliver remarks calling for a new U.S. policy on Israel and Palestine elsewhere, but he could have used his sway and platform to instead target a national security issue where policy changes are more viable, like pulling U.S. troops out of Afghanistan. “He ensured that it did not have nearly the impact it might have,” Bennis said.

She wants Sanders to focus on defending diplomacy, particularly in the face of proposed Trump administration cuts to the State Department, and shaming those seeking new conflicts, highlighting the failures of the 16-year U.S. Global War on Terror, she said.

Both believe Sanders is turning his attention to foreign policy at a time when the U.S. public ― particularly young people to whom the senator is particularly appealing ― is ready to see American power in fresh ways. Younger Americans now see domestic problems in the U.S. as inherently tied to international issues, Hurlburt noted.

Building momentum for change ― and new leaders who can effect change, like potentially Sanders ― now rests on tactics like getting anti-militarism information to activists organizing against white supremacy, unfettered capitalism and misogyny, Bennis said, and establishing new coalitions around shared interests.

“War is racist to the core,” she said.