Potential Clinton opponents ponder their options

We should know within the next several months how many challengers Hillary Clinton will face in next year's Democratic primaries.

Four potential candidates -- Martin O'Malley, Bernie Sanders, Jim Webb and Lincoln Chafee -- have said in recent days they will decide soon on 2016 presidential bids.

"I'm very seriously considering that," said O'Malley, the former governor of Maryland, speaking on CBS' Face The Nation.  "And I'll make up my mind by the end of May."

Sanders, an independent senator from Vermont, told Fox News Sunday that "we're working on it and we'll make the best decision we can within the near future."

Webb, a former senator from Virginia, also did not provide a specific timeline, telling CNN's State of the Union that "we are looking at it and looking at it hard."

Chafee, a former senator and governor from Rhode Island, already sounds like a candidate, telling CNN last week "I'm running," though aides noted that the official paperwork has not yet been filed.

Then there's Vice President Biden, who says he hasn't decided on whether to run for the top spot, or when to make an announcement.

"There’s a lot the president and I care about that has to get done in the next two, three months," Biden told reporters last week.  "And when you’re running for president, you got to run for president. And I’m not ready to do that, if I’m ever going to be ready to do it.”