Third-party voters are the ones to watch as we head toward Election Day

DENVER -- As some polls show the race for president tightening, third-party candidates may be the ones to watch this election.

"There's often some tightening up that occurs in the weeks before Election Day," said University of Denver political scientist Seth Masket.

Masket says we could be seeing a shift from third-party voters -- in many cases Libertarians who now may be leaning Republican.

"It's pretty common for voters to move away from third-party candidates two weeks before the election and for that support to go to some of the other candidates," he said.

Some polls release this week show a dip in overall percentages for Libertarian Gary Johnson and Green Party candidate Jill Stein, which some say signal that people who had been supporting either of the two are shifting toward voting for Democrat Hillary Clinton or Republican Donald Trump.