Robbie Mook, Hillary Clinton's campaign manager, is raising the alarm: Bernie Sanders is doing very well.

"Late last night, Bernie Sanders' campaign announced they'd raised $1.4 million from 50,000 donations in a single day. The day before, they announced that the Reddit community had contributed more than $1 million to his campaign," Mook writes in an urgent email to supporters.

"There's no denying this: His supporters are stepping up. They see a chance to win in Iowa and they're willing to go all in for their guy. Hillary can't do this if you're on the sidelines, Daniel. You need to step up and match them.

"If Donald Trump takes the Republican nomination, our party will lose more than the presidency. Years of progress will be ripped away. Obamacare will be repealed. Marriage equality will be rolled back. Get excited to visit the wall on the Mexico border -- and get ready to pay for it if President Trump can't magically get Mexico to cough up the cash for it.

"That's what's at stake here. It's about the future of our country. We can't let Bernie Sanders' supporters out-match us. It's not just about the nomination. It's about what comes next.

"Hillary's counting on you. Chip in $1 before the Iowa caucuses on Monday."