Note it states 2/3rds of those "present and voting".  Perhaps a quorum is also required first to provide base.  435 Seats, quorum = 1/2 + 1 = 218.  There are 198 Republicans and 235 Democrats within todays' House, with 2 positions currently vacant,  37 more Dems than Repubs.  Not sure the disposition of the 2 vacancies. Given that, quorum would be 433 / 2 + 1 = 217.  2/3rds of 217 = 145, giving the 198 Repubs enough to oust under current seating with minimal quorum present and voting. That takes only 19 Dems.