While he voted against the passage of the landmark legislation,<ref>[https://www.govtrack.us/congress/votes/88-1964/s409 HR. 7152. PASSAGE.]. ''GovTrack.us''. Retrieved February 18, 2021.</ref> he voted in favor of invoking cloture to end the filibuster led by Southern Democrats<ref>[https://www.govtrack.us/congress/votes/88-1964/s302 HR. 7152. MANSFIELD DIRKSEN MOTION THAT THE SENATE INVOKE CLOTURE ON THE SOUTHERN FILIBUSTER.]. ''GovTrack.us''. Retrieved February 2021.</ref> at the urging of Republican [[Senate Minority Leader]] [[Everett Dirksen]].<ref>[https://www.nytimes.com/1964/06/01/archives/hickenlooper-opposes-closure-till-rights-bill-is-modified-more.html Hickenlooper Opposes Closure Till Rights Bill Is Modified More]. ''The New York Times''. Retrieved February 18, 2021.</ref> This was despite previously being hesitant towards cloture.<ref>[https://www.nytimes.com/1964/06/01/archives/hickenlooper-opposes-closure-till-rights-bill-is-modified-more.html Hickenlooper Opposes Closure Till Rights Bill Is Modified More]. ''The New York Times''. Retrieved May 23, 2021.</ref> | While he voted against the passage of the landmark legislation,<ref>[https://www.govtrack.us/congress/votes/88-1964/s409 HR. 7152. PASSAGE.]. ''GovTrack.us''. Retrieved February 18, 2021.</ref> he voted in favor of invoking cloture to end the filibuster led by Southern Democrats<ref>[https://www.govtrack.us/congress/votes/88-1964/s302 HR. 7152. MANSFIELD DIRKSEN MOTION THAT THE SENATE INVOKE CLOTURE ON THE SOUTHERN FILIBUSTER.]. ''GovTrack.us''. Retrieved February 2021.</ref> at the urging of Republican [[Senate Minority Leader]] [[Everett Dirksen]].<ref>[https://www.nytimes.com/1964/06/01/archives/hickenlooper-opposes-closure-till-rights-bill-is-modified-more.html Hickenlooper Opposes Closure Till Rights Bill Is Modified More]. ''The New York Times''. Retrieved February 18, 2021.</ref> This was despite previously being hesitant towards cloture.<ref>[https://www.nytimes.com/1964/06/01/archives/hickenlooper-opposes-closure-till-rights-bill-is-modified-more.html Hickenlooper Opposes Closure Till Rights Bill Is Modified More]. ''The New York Times''. Retrieved May 23, 2021.</ref> |