walk out on~

米大統領選挙の指名争いがいよいよ本格化します。flip-flopと呼ばれたRomney候補者がここに来て、盛り返してきました。ライバルのBachmann候補の選挙参謀が寝返ったからだと言われています。ここではwalked out on herと表現されています。きつ〜いonの使い方ですね。（ゼミ生 Pear）
Mitt Romney hopes for Iowa win as rival Republicans wobble
Republican presidential nomination race rocked as Bachmann's Iowa campaign chair walks out on her

Republican front-runner Mitt Romney is showing increasing signs of optimism in the run-up to the Iowa caucuses on 3 January as the campaign of one of his rivals for the presidential nomination came close to imploding and others struggled.

Romney has belatedly devoted time and money to Iowa, which he initially ignored, and could be rewarded with a first or second place, according to polls published on Thursday.

The Rasmussen poll puts Romney on 23%, Ron Paul 22%, former senator Rick Santorum on 16%, former House speaker Newt Gingrich on 13% and Texas governor Rick Perry on 13%.

http://www.guardian.co.uk/world/2011/dec/29/mitt-romney-republican-nomination-iowa