Can polls in May predict the winner in November?

These polls can also have a big impact on fundraising, says Republican strategist Bruce Haynes.

“Donors like to support campaigns that they feel are going somewhere, that have an opportunity to win, that have that critical momentum behind them,” says Haynes.

And he says these early polls also can mobilize people who don’t give money.

“They generate momentum in terms of energy around the campaigns, how are volunteers looking at the campaign,” says Haynes. “Is this a campaign that I want to support, knock on doors for, put a bumper sticker on my car for?”

So while running poorly in polls can kill a candidate, getting too far ahead can hurt, too.