A top GOP senator and ally of President Donald Trump said he thinks special counsel Robert Mueller "is the best person to look at" whether the president may have tried to obstruct justice through any possible interference with the Russia investigation.

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PHOTO: Sen. Lindsey Graham arrives to vote on the confirmation of Samuel Brownback, governor of Kansas and a former U.S. senator, to become the ambassador-at-large for international religious freedom, at the Capitol in Washington, D.C., Jan. 24, 2018. — Sen. Lindsey Graham arrives to vote on the confirmation of Samuel Brownback, governor of Kansas and a former U.S. senator, to become the ambassador-at-large for international religious freedom, at the Capitol in Washington, D.C., Jan. 24, 2018.

"Mr. Mueller is the perfect guy to get to the bottom of all this," Sen. Lindsey Graham, R-S.C., told ABC News' "This Week" Co-Anchor Martha Raddatz on Sunday.

PHOTO: Special Counsel Robert Mueller departs the United States Capitol following his closed-door meeting with top members of the U.S. Senate Committee on the Judiciary in Washington, D.C., June 21, 2017. — Special Counsel Robert Mueller departs the United States Capitol following his closed-door meeting with top members of the U.S. Senate Committee on the Judiciary in Washington, D.C., June 21, 2017.

Graham was referring to questions around whether Trump's having considered firing Mueller last year may constitute obstruction of justice. Mueller leads the federal investigation into Russia's alleged meddling in the U.S. election and possible ties to Trump associates.

"I have complete confidence in Mr. Mueller," Graham said.

PHOTO: President Donald Trump arrives to delivers a speech to the World Economic Forum, Jan. 26, 2018, in Davos. — President Donald Trump arrives to delivers a speech to the World Economic Forum, Jan. 26, 2018, in Davos.