A Republican senator wants to know whether the FBI warned the Trump campaign about Russian attempts to infiltrate the campaign.

Bombshell revelations this week about former Trump campaign chairman Paul Manafort are what prompted the inquiry, made by the Senate Judiciary Committee chairman Chuck Grassley to FBI Director Christopher Wray.

In a letter to Wray, Grassley asks whether the FBI ever provided a “defensive briefing” or any other warnings about “attempts to infiltrate the campaign by people connected with, or compromised by, Russian intelligence.”

“Such a briefing allows innocent, unwitting organizations and individuals to take defensive action to protect themselves,” Grassley wrote to Wray.

Several reports have come out this week about Manafort, a longtime Republican political consultant. CNN reported on Monday that U.S. investigators were conducting surveillance on Manafort before and after the presidential election. The surveillance picked up Manafort discussing the campaign with Russian operatives.

Investigators obtained a secret Foreign Intelligence Surveillance Act warrant on Manafort just after he left the Trump campaign in August, The Wall Street Journal reported Thursday night.

On Wednesday, The Washington Post reported that just after joining the Trump team last April, Manafort sent emails offering to provide a “private briefing” about the state of the campaign to Oleg Deripaska, a Russian oligarch closely connected to Vladimir Putin.

Manafort has business ties to Deripaska that stretch back over a decade. The two were recently involved in a dispute over unpaid debts. Manafort’s emails, which were sent from his campaign address, suggested that he sought to use his campaign position to settle the financial dispute.

Manafort’s activities raise the question “of whether the FBI ever alerted Mr. Trump to the FBI’s counter-intelligence concerns regarding his campaign manager and others associated with the campaign,” Grassley writes in his letter to Wray.

Grassley asserted that the FBI often uses defensive briefings to “thwart attempts by foreign intelligence services to infiltrate organizations or compromise U.S. citizens.”

The Iowa Republican also noted that Manafort has been at the center of one such defensive briefing.

He pointed to a report out earlier this year that in 2008, U.S. intelligence raised concerns about Manafort’s foreign consulting work to Arizona Sen. John McCain’s presidential campaign.

Manafort’s business partner, Rick Davis, was McCain’s campaign manager. At the time, Manafort and Davis were working on behalf of then-Ukrainian Prime Minister Viktor Yanukovych. The business partners also arranged two meetings between McCain and Deripaska, the Russian oligarch who Manafort offered to brief last year.

Grassley told Wray that the circumstances that prompted a defensive briefing to McCain’s campaign about Manafort’s work “seem substantially similar” to the situation surrounding the Trump campaign.

Grassley says that any warning by the FBI to the Trump campaign would raise the question of how the Trump team responded.

“On the other hand, if the FBI did not alert the campaign, then that would raise serious questions about what factors contributed to its decision and why it appears to have been handled differently in a very similar circumstance involving a previous campaign,” writes Grassley.

WATCH REP. ADAM SCHIFF LAY OUT CONNECTIONS BETWEEN TRUMPS AND RUSSIA DURING CAMPAIGN:

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