The super PAC supporting Sen. Marco Rubio's presidential bid has prepared its first television advertisement, one that seems to be preparing for the possibility of more attacks from former Florida Gov. Jeb Bush.

At the same time, Conservative Solutions PAC dismissed Bush as an already failed candidate on Friday in a memorandum the group sent to donors and supporters that was obtained by the Washington Examiner.

"When you consider all angles, as we do, we believe there are really only four candidates with a reasonable chance of becoming the Republican nominee: Senator Marco Rubio, Dr. Ben Carson, Donald Trump, and Senator Ted Cruz. And when you look on to the general election against Hillary Clinton, we are convinced that Marco gives the GOP its best chance to win," wrote the super PAC's lead strategists, Warren Tompkins and Jon Lerner.

Notably, there's no mention of Bush, the former front-runner who has begun taking aim at fellow Floridian Rubio as part of his strategy for climbing back into contention in the race for the 2016 Republican nomination. Bush's independent super PAC, Right to Rise USA, also has started attacking Rubio.

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