Washington, Jul 16 (IANS): Democratic Party's presumptive presidential nominee Hillary Clinton is leading Republican rival Donald Trump in four crucial swing states, a new poll has revealed.

A swing state is a US state where the two major political parties have similar levels of support among voters, important in deciding the final result of a presidential election.

The NBC News/Wall Street Journal/Marist poll issued on Friday found Clinton with high single-digit leads in Colorado, Florida, North Carolina and Virginia, CNN reported.

Clinton leads Trump in Colorado 43 per cent to 35 per cent, the poll showed.

In Florida, Clinton also paced Trump, 44 per cent to 37 per cent. Clinton was ahead of Trump in North Carolina 44 per cent to 38 per cent, a state which President Barack Obama won for Democrats in 2008 for the first time since 1976.

Finally, Clinton led Trump comfortably in Virginia, 44 per cent to 35 per cent, CNN reported citing the poll.

Meanwhile, a poll conducted by Quinnipiac University, Connecticut, released earlier this week for Florida, Pennsylvania, Ohio, and Iowa, showed closer races, with Trump leading or tied with Clinton.

In Florida, Quinnipiac found Trump up 3 percentage points to Clinton, 42 per cent-39 per cent.

However, both the surveys found about one in five voters in Florida were undecided or did not support either Trump or Clinton, CNN noted.

The NBC News/Wall Street Journal/Marist poll was conducted from July 5 through 10, and surveyed 871 registered voters in Florida, 907 in North Carolina, 876 in Virginia, and 794 in Colorado.

The margin of error is plus or minus 3.3 points in Florida, North Carolina and Virginia, and 3.5 points for Colorado.