LEWISTON — At least two key races are very tight as voters head to the polls across Maine.

Political insiders from both parties said Monday that Maine’s hotly contested 2nd Congressional District race is impossible to predict.

“Every vote tomorrow will make the difference,” Democrat Emily Cain told supporters at her Lisbon Street headquarters Monday.

Republican Mayor Robert Macdonald said it’s likely to be a close one as U.S. Rep. Bruce Poliquin seeks to hang on to the seat he defeated Cain to win two years ago.

On a national level, many eyes are on the same district because of the slim possibility it could make the difference in whom sits in the White House next year.

Politico said northern Maine is one of “16 battlegrounds that will decide the election” because GOP presidential hopeful Donald Trump has enough strength in Poliquin’s district to have a decent shot at picking up one electoral vote the district’s winner is assigned.

If that happens, it will be the first time Maine has split its presidential electors since adopting the system in 1972 and one of the few times in American history that a state’s Electoral College delegation is divided.

Trump is facing long odds nationally in his quest to beat Democrat Hillary Clinton, who leads in nearly every poll. But some possible scenarios have it all coming down to who wins Maine’s 2nd District.

Former Maryland Gov. Martin O’Malley, who fell short in his Democratic presidential bid, made a campaign swing through Lewiston on Monday on Clinton’s behalf.

He said the presidential contest offers “a stark choice between freedom and fascism.” He said Trump represents “a real grave threat to our country.”

But Trump has fans who see him in a different light entirely.

For Jeff Schmidt of Mechanic Falls, Trump offers the possibility of a better economy.

“I’m glad he’s battling for every vote he can get. He’s going to need them,” said Schmidt, a shoemaker.

In addition to the presidential and congressional races, voters will decide five controversial ballot questions, including measures that would legalize recreational marijuana and hike the minimum wage, and a number of state legislative contests.

It is possible to register and vote until the polls close at 8 p.m.