Trump rally in Cleveland
Trump rally in ClevelandReuters

US voters are still swinging, as new polls which include third-party candidates show a significantly narrower gap between presidential nominees Donald Trump and Hillary Clinton.

A wave of recent polls, especially in swing states, show that when voters are offered a four-way race - involving Trump, Clinton, Libertarian Party candidate Gary Johnson and Green Party candidate Jill Stein - Hillary Clinton often falls while Trump remains steady.

The results come as Stein hammers away at disillusioned Democratic supporters, inviting Bernie Sanders supporters to choose her as an alternative to their chosen, but fallen, candidate.

In Virginia , a new Washington Post polls shows Clinton leading a two-man race by 14 points. When surveyors included Johnson and Stein in their question, though, Clinton's lead dropped to 11 points.

Quinnipiac University studies in the swing states of Florida, Ohio, and Pennsylvania showed a similar pattern - the races get tighter when Johnson and Stein are served up as presidential possibilities.

"When voters are asked about a four-way ballot that includes Libertarian Gary Johnson and Green Party nominee Jill Stein, Trump picks up a point or two against Secretary Clinton in each of the three states,” Peter A. Brown, assistant director of the Quinnipiac University Poll, said in a statement.

A new NBC News national poll shows similar results: Clinton’s 9-point lead shrivels to 6 points when Johnson and Stein are included.