Sen. Ben Sasse, R-Neb., who has staked out a leading role as a Donald Trump critic, and Ohio Gov. John Kasich are the top prospects being courted to run as an independent candidate against Trump and Hillary Clinton.

Mitt Romney, the Republican’s 2012 presidential nominee, is among a group of Republicans actively leading the independent candidate effort, according to a Washington Post report. Sources tell the Post Romney has personally reached out to both men in recent days.