LAS VEGAS (REUTERS) - Democratic presidential candidate Bernie Sanders unintentionally conjured a reference to one of his Republican rivals during a campaign rally in Las Vegas, Nevada, on Sunday (Feb 14).

Mr Sanders used the word "huge" when talking about the influence that big donors have on US politics.

Enthusiastic supporters then echoed the word, drawing it out in the manner of Republican presidential candidate, Mr Donald Trump.

Mr Sanders' face turned red as he grinned and shook his head at the crowd.

Since the beginning of the year, Mr Sanders has erased former Secretary of State Hillary Clinton's wide lead for the Democratic presidential nomination, putting the two in a dead heat nationally, according to a Reuters/Ipsos poll.

Mrs Clinton leads Mr Sanders 48 per cent to 45 per cent among Democratic voters, according to the poll of 512 Americans, conducted from Feb 2-5 after the Iowa caucus. The poll has a credibility interval of 5 percentage points.

After scoring a virtual tie in the Iowa caucuses, and a victory in New Hampshire, Mr Sanders is now wooing voters in the states scheduled to hold the next round of voting.