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Every U.S. attorney and assistant U.S. attorney takes an oath of office when being sworn in. It's an oath to support and defend the Constitution of the United States against foreign and domestic enemies.

All federal prosecutors who take this oath share a deep commitment to the rule of law and the federal government's role in protecting public safety, promoting social justice and defending the rights and liberties of our citizenry. It is an oath I took when I twice served as U.S. attorney for Minnesota.

I was appointed to the position by President George H.W. Bush in 1991 and again by President George W. Bush in 2001. I was not asked to be a Republican U.S. attorney. I was not asked to use my office to investigate the president's political opponents. Although I was a political appointee, it was expected that politics would play no role in the exercise of my office's prosecutorial discretion.

But I fear that's what has happened under the current administration. And unless we elect former Vice President Joe Biden and Sen. Kamala Harris, I worry about what our nonpartisan career prosecutors will be asked to do on behalf of President Donald Trump.

Since coming into office, Trump has politicized the Department of Justice (DOJ) beyond recognition. Based on his actions and his statements it is clear he sees the attorney general as his personal attorney, and he believes the DOJ should investigate and prosecute his political opponents.

The people who work at the DOJ in Washington, D.C., and the prosecutors in U.S. attorneys offices nationwide are not partisan warriors. They've served under Republican presidents and Democratic presidents alike. I never asked any lawyer who they voted for before hiring them. Can the president say the same thing?

U.S. attorneys are the chief federal law enforcement officers in their respective states. As such, they are expected to work closely with state and local officials of any and all political affiliations to promote social justice and to build an effective and impartial law enforcement system.

Unfortunately, Trump has undermined the DOJ's ability to lead and unify by picking political fights with state and local officials in a way that demoralizes and attempts to cast blame.

In contrast to Trump's efforts to politicize and divide, Biden has devoted his career to supporting law enforcement and has long said his DOJ will be independent and impartial. A Biden DOJ will only be guided by the law and the facts. Biden's commitment to a fair and effective justice system is underscored by his decision to pick Harris, a former district attorney and state attorney general, as his running mate.

Harris recognizes the importance of independent, competent prosecutors. I expect a Biden-Harris administration will restore the public's confidence in the DOJ by focusing on its nonpartisan and unifying traditions.

This is important because the work of the department has never been more important. We must address the deep, structural issues and inequities that have long plagued our society. We must restore the trust between law enforcement officials and the communities they serve. We must use the department's resources and reach not to go after political opponents, but rather, true criminals.

We won't be able to do any of that in a second Trump term. Voters hold presidents accountable. If Trump is re-elected, if he no longer has to face voters again and can do whatever he pleases, what would he ask career prosecutors and DOJ leadership to do? Who would he send them after?

Joe Biden has said he wants to unite the country and be a president for all Americans. That would be a stark departure from what we have now. For the integrity of our justice system, the promotion of social justice, and the men and women in law enforcement and prosecutor's offices, we must elect Joe Biden and Kamala Harris.

Thomas Heffelfinger was the U.S. attorney for Minnesota from 1991 to 1993 and from 2001 to 2006.