Countdown to 2016: What We Know About When Potential Presidential Candidates Will Announce

— -- With the 2016 presidential race heating up, tracking all the potential candidates can keep your head spinning.

Though the list of possible White House hopefuls is growing by the day, no one has officially declared -- yet.

Here's the cast of characters likely to be a part of the 2016 contest, and a look at what we know about when they plan to make it official:

Democrats

Hillary Clinton

Announcement expected by: July

Former Secretary of State Hillary Clinton, who lost the Democratic nomination to Barack Obama in 2008, said last September that -- hypothetically -- if she were to consider running for president again, “I am going to be making a decision probably around the first of the year.”

Although we don’t yet know whether she has made up her mind, it certainly seems like all systems are go.

Politico, citing "top Democrats," reported on Jan. 29 that Clinton could delay any official announcement until June, which would allow her to continue sculpting her campaign in private. According to Politico, Clinton could announce an exploratory committee in April.

Jim Webb

Announcement expected by: January or February

Former Sen. Jim Webb was the first potential 2016 candidate to launch an exploratory committee last November. In an appearance at the National Press Club last September, he said discussions about his potential run would continue through January or February.

Bernie Sanders

Announcement expected by: March

Independent Sen. Bernie Sanders of Vermont told the Associated Press in December that he would make a decision about running for president by March of this year. Sanders returned earlier this month to New Hampshire, a first-in-the-nation primary state, telling NH1 that he is seriously considering a White House run.

Republicans

Rick Perry

Announcement expected by: May or June

Former Texas Gov. Rick Perry, who also ran in 2012, will announce his intentions in the 2016 presidential race in May or June, he told The New York Times. He held a series of fundraisers last November where he was likely met with potential supporters and Republican operatives, according to Politico.

Jeb Bush

Announcement expected by: Unknown

Former Florida Gov. Jeb Bush announced in a Facebook post in December 2014 that he would “actively explore the possibility of running for President.”

Though he hasn't publicly set a timeline for a formal announcement, Bush met with Mitt Romney earlier this month, fueling speculation that the two potential rivals were discussing their possible campaigns. Bush launched a leadership PAC called “Right to Rise” on Jan. 6.

Ted Cruz

Announcement expected by: June

Tea Party darling Sen. Ted Cruz, who says he believes that the field of GOP candidates will solidify in June, said on “Fox & Friends” that he is looking at a campaign very seriously.

Cruz has certainly proceeded as if he is already a candidate for 2016, visiting early primary states such as Iowa and New Hampshire, expanding his staff, and even renouncing his Canadian citizenship.

Chris Christie

Announcement expected by: May or June

New Jersey Gov. Chris Christie is expected to make a final decision about 2016 by “the end of the Spring,” according to Time Magazine. He launched a political action committee, Leadership Matters for America, on Monday Jan. 26.

Marco Rubio

Announcement expected by: March to May

A Rubio senior adviser told ABC News that Rubio has told them to “proceed as if he is running for president.” According to two unnamed Republicans, Rubio told about 30 core supporters that he would decide by the spring about whether or not to run for president.

Rand Paul

Announcement expected by: March to May

Kentucky Sen. Rand Paul confirms he will certainly be on the ballot in 2016 -- but hasn't officially declared whether it will be as a presidential candidate or merely a Senator. In September 2014, Paul announced that he will not make a decision about 2016 until the spring. He told the The Washington Times that ultimately, his decision to launch a bid will be depended on GOP’s willingness to endorse a “new kind” of Republican.

Scott Walker

Announcement expected by: June

Gov. Scott Walker established a political committee called “Our American Revival” on Tuesday, Jan. 27 that will help with his presidential campaign, according to the Associated Press. A Walker aide told ABC News that the governor plans to wait until late spring or summer to decide on 2016. He will most likely make his official announcement around June.

Ben Carson

Announcement expected by: May

Dr. Ben Carson said on ABC's This Week with George Stephanopoulos that he would make a decision about running for president by May 1.

Despite a busy schedule, and the formation of a political action committee, “One Nation”, he says he's not ready to make any commitments to a presidential campaign yet. "I don't know what my role will be in the future," Carson said, "but I know that I will continue to fight extremely hard for these principles."

Rick Santorum

Announcement expected by: Spring

The former senator from Pennsylvania has been busy traveling to important primary states and actively engaging with donors and activists this past year. Although, an aide said Santorum won’t make a final decision on a bid until later in the spring, all signs point to another run for the White House.

Lindsey Graham

Announcement expected by: Unknown

Sen. Lindsey Graham launched an exploratory committee Jan . 29 to “test the waters” for a potential 2016 run. His supporters include 2008 GOP nominee Sen. John McCain, who has publicly supported his candidacy: “My illegitimate son Lindsey Graham is exploring that option,” McCain joked in a news conference earlier this month. “I am strongly encouraging Senator Lindsey Graham particularly with the world the way it is today."