CAIRO — Egyptian security forces on Wednesday captured Essam el-Erian, one of the last few prominent leaders of the Muslim Brotherhood still at large after a crackdown that began with the ouster of President Mohamed Morsi, another of the group’s leaders.

The seizure of Mr. Erian, a senior leader in the Brotherhood’s political arm and an adviser to the president, appears to complete the incarceration of the organization’s most visible leaders less than 18 months after they stood on the brink of consolidating power over the presidency and Parliament. He was among the most outspoken leaders of the Brotherhood, Egypt’s mainstream Islamist movement, and his arrest caps a career that has traced the group’s evolution through years of repression, internal overhauls, electoral victories and political failure.

“He epitomized the swagger and overreach of the Muslim Brotherhood after the revolution,” said Mona el-Ghobashy, an Egyptian political scientist at Barnard who has studied the group. “It was like he was showing off, ‘We are the biggest party around and we are in power now.' ”

The authorities said they had arrested Mr. Erian after 26 failed attempts and finally found him in a villa in a Cairo suburb, according to state news media. Mr. Erian, who put up no resistance, looked gaunt and wore a white robe in pictures that circulated after he was detained.