The reason I believe William Barr’s nomination should be withdrawn has little to do with his experience. As attorney general for President George H.W. Bush, he has long been well-respected within the legal community. But the nominee for our nation’s highest law enforcement position must be measured by more than his résumé.

Nor is this a question of politics — which party can “win” Barr’s confirmation fight — but rather a question of character and fidelity to the Constitution. Will Mr. Barr rise to the defining challenge for an attorney general in the Trump era and defend the rule of law?

Based on his actions in the months before his nomination, I believe the answer is no.

Last June, Mr. Barr wrote a secret, unsolicited memo attacking special counsel Robert Mueller’s investigation into potential obstruction of justice by the president, which Mr. Barr then passed to administration officials.

In November, President Donald Trump fired Attorney General Jeff Sessions after months of public abuse over the Mueller investigation. For a temporary replacement, he chose Matt Whitaker, whose primary qualification appears to be an op-ed he wrote decrying the scope of the Mueller probe.

With Mr. Barr’s nomination, it has become clear that the president’s sole concern is choosing a new attorney general who will shield him from the special counsel’s investigation. And Mr. Barr’s memo looks much more like a job application.

Special counsel Mueller’s investigation into Russia’s attack on our democracy has led to numerous indictments and convictions, including that of the president’s own campaign chairman. It must continue free from political interference until it gets to the truth.

In the meantime, our country deserves better than an attorney general who auditioned for the job by attacking that investigation. Under our constitutional system, no one is above the law, not even the president. We need an attorney general willing to vigorously defend this principle.

Sen. Mark Warner, D-Va., is vice chair of the Intelligence Committee.