Donald Trump [Photo: agencies]

GOP presidential candidate Donald Trump ignited a political firestorm Saturday by questioning whether Sen. John McCain -- who spent over five years as a prisoner during the Vietnam War -- is a war hero.

Trump said he's a war hero because he was captured, and that quote- likes people that weren't captured.

By mid-afternoon, Trump tried to walk back his blunder on Twitter, saying "captured or not, all our soldiers are heroes!"

But his attempt at damage control seemed unlikely to diminish the anger his remarks had caused.They provoked an immediate outcry from his 2016 presidential rivals and the Republican National Committee, which has expressed concern about the impact his controversial remarks on immigration have had on the GOP brand.