WASHINGTON — A group of high-profile Republican strategists is working with a conservative billionaire on a proposal to mount one of the most provocative campaigns of the “super PAC” era and attack President Obama in ways that Republicans have so far shied away from.

Joe Ricketts, Chairman and Founder, Ameritrade

Timed to upend the Democratic National Convention in September, the plan would “do exactly what John McCain would not let us do,” the strategists wrote.