As the Senate Judiciary Committee advanced the nomination of Judge Brett Kavanaugh to the Senate floor, it seems that Democrats and left-wing pundits may very well (thanks to Arizona Sen. Jeff Flake) get what they've been asking for: an investigation by the FBI into the accusations of sexual assault against the nominee. But recent history casts doubt on whether a finding in Kavanaugh's favor would make a difference in the minds of Democrats who decided — long before there was any mention of the allegation — that Kavanaugh was unfit to serve on the Supreme Court.

Sens. Richard Blumenthal of Connecticut and Kamala Harris of California explicitly said that they believed the accuser, Christine Blasey Ford, and the rest of the Democrats on the Senate Judiciary Committee made pretty clear that they did, too. Senate Minority Leader Chuck Schumer made clear within minutes of Kavanaugh's nomination in July that the Democrats would oppose him. So what would an FBI investigation change? An FBI finding in Kavanaugh's favor will not open Senate Democrats up to his ideas on originalism and Chevron deference. Yet, the Judiciary Committee Democrats insist that the cloud could be lifted, if only Kavanaugh joined them in calling for an FBI investigation. And they've talked Sen. Flake into believing them.

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However, Senate Democrats would almost surely ignore or dismiss any exculpatory conclusions drawn by the FBI. We know this because it has happened before. When then-Supreme Court nominee Clarence Thomas sat before the same committee, accused of sexual harassment, then-Sen. Joe Biden told the world what he thought about the FBI's report of its investigation into Thomas:

The next person who refers to an FBI report as being worth anything obviously doesn't understand anything. FBI explicitly does not, in this case or any other case, reach a conclusion, period. Period. … They say, he said, she said and they said, period . . . So when people wave an FBI report before you, understand they do not — they do not, they do not — reach conclusions. They do not make, as my friend points out more accurately, they do not make recommendations.

But that's not the only time that the Left has shown indifference to the conclusions of investigations undertaken by the Department of Justice, when those findings conflict with its political agenda. I recently attended a panel discussion at a pop-up Museum of Broken Windows in Manhattan. During the discussion, one of the panelists pointed to the decision not to charge then-officer Darren Wilson for the shooting of Michael Brown in Ferguson, Mo., in 2014, as indicative of the systemic bias and injustice that activists must mobilize to fight. Among progressive police critics, Ferguson continues to be a rallying cry and symbol of unjustified police violence — though the Department of Justice cleared Wilson of any wrongdoing the following year. Indeed, the DOJ (led then by Attorney General Eric Holder) concluded in an extensive report that "[t]he physical evidence establishes that Wilson shot Brown …  while Wilson sat in his police SUV, struggling with Brown for control of Wilson's gun," and that "[t]here [were] no credible witness accounts that state that Brown was clearly attempting to surrender when Wilson shot him." Yet cries of  "Hands up, don't shoot," Brown's apocryphal last words, are still heard at police protests.

Why, then, should Kavanaugh, Flake, or anyone else, believe that an FBI investigation into the accusations made against him would do any good with Democratic senators? It didn't help Clarence Thomas. It hasn't stopped people from pointing to Michael Brown as a victim of racially biased brutality. And when it comes to the fate of Judge Brett Kavanaugh, whose mind would it change?

Rafael A. Mangual is a fellow and deputy director of legal policy at the Manhattan Institute for Policy Research, where he focuses on issues related to criminal justice reform. This piece originally appeared in City Journal.