Was Mueller the right choice for special counsel in Russia investigation?

WATCH: Who is Robert Mueller, the man appointed by the Justice Department to oversee the investigation into possible ties between Russia and President Trump's campaign? Garrett M. Graff, author of "The Threat Matrix," joined Daniel Bush to take your questions.

Posted by PBS NewsHour on Thursday, May 18, 2017

Former FBI director Robert Mueller is back in the spotlight, with his appointment Wednesday as the special counsel in charge of the federal investigation into Russia’s interference in the 2016 election and possible collusion with Donald Trump’s campaign.

The selection of Mueller, who lead the agency from 2001 to 2013, drew praise from Democrats and Republicans in Washington. But President Trump criticized the appointment in a statement Wednesday and again at a White House news conference Thursday.

“I look forward to this matter concluding quickly,” Mr. Trump said in the statement.

But Mueller’s investigation could go on for a while, according to Garrett Graff, the author of the 2011 book “The Threat Matrix: The FBI at War in the Age of Global Terror,” an inside look at the FBI and Mueller’s tenure at the agency.

“FBI investigations are not fast, and Bob Mueller is unlikely to launch a particularly fast investigation,” Graff told me in an interview Thursday.

A lengthy probe could “really paralyze Donald Trump’s agenda as long as his staff is consumed by this investigation and as long as Bob Mueller is out there toiling away,” Graff added.

As Mueller prepares to wade into the controversy, I sat down with Graff to talk about Mueller’s career and how he might handle the Russian investigation. Watch our conversation in the player above.