O'Malley joins the 2016 race to challenge Clinton, but can he win?

Former Maryland Gov. Martin O'Malley announced Saturday that he's joining the Democratic field as a presidential candidate, joining Vermont Sen. Bernie Sanders in challenging Hillary Clinton. She has better name recognition and more money, so what makes either of them think they can beat the frontrunner for the Democratic nomination?

They face a huge gap in support that seems tough to tackle even in the 13 months until next year's convention.

Clinton was the frontrunner in 2007 too, but at this point in the race, her opponents weren't all that far behind.

It's an uphill battle, but for the Democrats challenging her, but it starts with showing voters how they're different.

Of all the Democratic hopefuls in this race, Bernie Sanders probably won't have a tough time distinguishing himself — after all, he's not even a Democrat, he's a Democratic Socialist.

Even if he doesn't exude the typical charisma of a politician, the Vermont senator could push Clinton to the left on some issues.

But he and the Democratic party at large do have one common enemy: Wall Street.

Martin O'Malley especially has tried to tie that vilified financial class to both Hillary Clinton and Jeb Bush.

"I've got news for the bullies of Wall Street: The presidency is not a crown to be passed back and forth by you between two royal families," O'Malley said in his campaign announcement.

That issue could be a sensitive subject for Clinton and the Democratic base. After all, her biggest donors throughout her career include Goldman Sachs and JP Morgan.

O'Malley, Sanders and whoever else jumps into the race will try to turn their one big weakness into an advantage.

Their hope is that low support and lower name recognition doesn't mean their ideas have been rejected. It just means voters haven't heard those ideas yet.