(Associated Press Photo)

WASHINGTON (AP) — FBI Director Christopher Wray's appearance before a Senate committee could be something of a preview of the intense questioning special counsel Robert Mueller is likely to face in Congress the next day.

Wray is set to testify Tuesday morning before the Senate Judiciary Committee, which is chaired by one of President Donald Trump's closest allies, Sen. Lindsey Graham. The South Carolina Republican has vowed to investigate the origins of the Russia investigation.

Republicans are likely to spend time questioning Wray and Mueller about Peter Strzok, an FBI agent who helped lead the Trump investigation and exchanged anti-Trump text messages during the 2016 election with an FBI lawyer, Lisa Page.

Once Mueller learned of the existence of the texts, which were sent before his appointment as special counsel, he removed Strzok from his team investigating potential ties between Russia and the Trump campaign. Strzok ultimately was fired , and Page left the bureau.

Wray made headlines during a Senate hearing in May when he broke from Attorney General William Barr and said he didn't consider court-approved FBI surveillance to be "spying" and that there was no evidence the FBI illegally monitored Trump's campaign during the 2016 election. Barr has said he believes "spying did occur" on the campaign and suggested the origins of the probe may have been mishandled.