Mitt Romney’s lead in national polls has narrowed after a comeback by Newt Gingrich, according to two surveys that could energise his rivals who are scrambling to prevent him from quickly clinching the Republican presidential nomination.

A survey by Rasmussen released on Wednesday showed Mr Romney still in first place among Republican voters, with 30 per cent of preferences. But Mr Gingrich, the former speaker of the House of Representatives, was trailing just three percentage points behind, at 27 per cent. A CBS/New York Times poll showed Mr Romney, the former Massachusetts governor, with a seven percentage point advantage over Mr Gingrich.