White House counselor Kellyanne Conway said Tuesday that national security adviser Michael Flynn resigned because he had misled Vice President Mike Pence.

“In the end, it was misleading the Vice President that made the situation unsustainable,” she said in an interview with TODAY on Tuesday.

“The incomplete information or the inability to completely recall what did or did not happen as reflected in his debriefing of particular phone calls — that really is what happened here.”

Flynn resigned Monday night and said that during the transition, he held “numerous” phone calls with foreign ambassadors, including the Russian ambassador to the U.S. He admitted that he had relayed “incomplete information” to Pence about his conversation with the Russian ambassador.

“He knew he had become a lightening rod, and he made that decision,” Conway said on TODAY.

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Write to Katie Reilly at Katie.Reilly@time.com.