Monica Malpass in New Hampshire: Narrowing Republican field

MANCHESTER, N.H. (WPVI) -- After Iowa's upsets, New Hampshire is more critical than ever.

On the Republican side: Will Donald Trump lose two in a row? Or will he win this one, and leave Ted Cruz, Marco Rubio and John Kasich to duke out the second and third spots?

"Right now Cruz is still trying to position himself, but Rubio is on his heels. If it's John Kasich, that means things will start to shift a little bit," said Nia Meeks, political analyst.

New Hampshire could narrow the Republican field by at least four or five candidates. Will Ben Carson, Chris Christie, Carly Fiorina, Jeb Bush and others keep battling on if they fare poorly?

Political analyst Ed Turzanski says Bush will likely stay until the end, but not the others.

"Christie had a very narrow path to the nomination. New Hampshire was critical there," said Turzanski. "If he doesn't place second or a close third, it may be over for him as well."

On the Democratic side, New Hampshire revived Mrs. Clinton's campaign back in 2008 after Barack Obama beat her in Iowa. She's hoping to repeat history, but Bernie Sanders' is doing his best to put a monkey wrench in that.

"Bernie Sanders, I'm very confident, will win New Hampshire, he's polling very well there. How well he does in terms of the margin of victory, I assume, he's really, really viable," said Jeff Jubilierer,political analyst.

"If he wins New Hampshire, I think the Democratic primary race continues for some time," said Terry Madonna of Franklin & Marshall College. "The Democrats use proportional allocation of delegates, so he could hang in for a while."

We'll be following the candidates Monday as they make their last dash looking for votes around New Hampshire.

Whoever wins or loses, it will certainly change the calculus of national politics within a matter of hours.