Vigenère cipher/Cryptanalysis

Vigenère cipher/Cryptanalysis is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Given some text you suspect has been encrypted with a Vigenère cipher, extract the key and plaintext. There are several methods for doing this. See the Wikipedia entry for more information. Use the following encrypted text:

ULACY ILOMA EDBXK DSERQ QZWEX JECTD WVOEL IQKIV
HXVSE YZXZH BTEVC AULAC YILOM AYDJN UIMTK EFKAY
YPTAX MVWTM GBASE PDXKZ RCAGZ OMKSQ KABZZ QYTSS
ANSTD BGOEP KPGUO KMOEM ALQCU BGTMW SGHXL VYIOX
KVZVW VEWAL FAALW ACDXW MMKLI CUHKA WFHCW ABSIK
UXZVC XLVAG WHWKU YXMQJ LVHHN NLVOI KAWFH VHXCH
FDLVO VKBAK TAXFI UVJXS IDIEA FXDLK MJDPV XXJRH
NNLVO ILBTX IAWHH KEPKF MYJCI FALBA GCTIG UMKAQ
OGXAA QHRVA PISWG ATUHV OVGBO YXJEO HYTCS FDHLV
AGNML UMERI JZVRG MHXEL JVPXV LIUEP DPBAL KAWZL
IULGW XGAKC SYEWP ZRIBT VR