The war in Iraq has roiled presidential politics in each election since President George W. Bush launched the invasion of the country in 2003. It was central to the 2004 election, arguably the reason that Barack Obama defeated Hillary Clinton for the 2008 Democratic nomination, and no small factor in Donald Trump s victory in 2016, when he pitched himself as an alternative to elites in both parties particularly his rivals in the GOP who had backed the invasion.

As Joe Biden leads the Democratic field for 2020, the U.S.s bloody history with Iraq is set to again become a defining issue in the race, and not simply because Trump has talked about an indefinite U.S. military presence there.

Biden wants to convince voters his resume on foreign policy is an asset. But theyve got ground to think otherwise.

Hes been wrong on nearly every major foreign policy and national security issue over the past four decades, former Defense Secretary Robert Gates, who served with Biden in the Obama administration, wrote in his 2014 book.

Just this month, Bidens primary opponents have zeroed in on his support for Bushs invasion.

Youve got to ask yourself where Joe Biden is on the issues that are most important to you. Did he support the war in Iraq that forever destabilized the Middle East? former Rep. Beto ORourke asked on MSNBC this week. Days earlier, Rep. Seth Moulton (D-Mass.) had called for Biden to apologize. Almost 30 percent of Democrats are unhappy about Bidens vote and more than 40 percent of party supporters younger than 30 say it makes them less likely to back him, a Politico/Morning Consult poll recently found .

And Bidens campaign isnt offering a counternarrative either about what he has learned from the past or what wisdom he will bring to bear on the current challenge. With more than 5,000 U.S. troops now in Iraq and analysts warning that reconciliation and stability after the defeat of the Islamic State will require painstaking work, what does he want to do next?

Bidens spokespeople did not respond to HuffPosts multiple requests for comment for this story, and Bidens former top advisers declined to speak.

The best guide, then, lies in Bidens history.