2016 gets real

It’s a big week for 2016.

Former Hewlett Packard CEO Carly Fiorina jumped into the race early Monday morning, declaring "I am running for President" on Twitter shortly after making an official announcement on ABC's "Good Morning America."

In a video posted online, Fiorina immediately painted herself as Hillary Clinton’s chief critic, beginning her video with a brief clip of the former secretary of state’s own presidential announcement. 

“Our founders never intended us to ah ave a professional political class,” she says in the video. “We know the only way to reimagine our government is to reimagine who is leading it. I’m Carly Fiorina and I’m running for president”

Later in the morning, around 10:30 a.m. ET,  retired neurosurgeon Dr. Ben Carson is expected to join the 2016 candidate pool with an announcement from Detroit. Carson confirmed Sunday evening to a local television station that he will seek the Republican nomination for president, the Associated Press reported.

"I'm willing to be part of the equation and therefore, I'm announcing my candidacy for president of the United States of America," Carson said in a pre-recorded interview with Ohio's WKRC. 

The Republican presidential field is likely to double in the next couple of days, as former Arkansas Gov. Mike Huckabee is also set to declare a White House bid on Tuesday. So far, the GOP field consists of Sens. Ted Cruz of Texas, Rand Paul of Kentucky, and Marco Rubio of Florida.

Related: Just how big will the 2016 field get?

On Friday, Huckabee released a video, entitled “Nailed Shut,” which is to introduce the Republican as a presidential candidate during his official announcement next week in Hope, Arkansas. The two-minute, 18-second spot casts the governor as a come-from-behind leader who fought “huge Democratic majorities” in his state and will continue to “fight for what matters most.”

“Every day of my life in politics was a fight, and sometimes it was an intense one,” says Huckabee, who won the Iowa caucuses during his 2008 presidential bid, in the video. “But any drunken redneck can walk into a bar and start a fight. A leader only starts a fight that he’s prepared to finish.” This would be the second presidential campaign for the Republican.

Fiorina’s official introduction as a presidential candidate, by contrast, is expected to be more low-key, with an announcement posted to social media, followed by visits to Iowa, New Hampshire, and South Carolina later in the week. A long-shot who has never held elected office, Fiorina will likely be the only Republican woman in the 2016 race.

Related: GOP message out of step with millennials

Carson’s chances of winning the Republican nomination are also low. According to polling data compiled by Real Clear Politics, Carson is trailing former Florida Gov. Jeb Bush, Wisconsin Gov. Scott Walker, Sens. Marco Rubio of Florida, Rand Paul of Kentucky and Ted Cruz of Texas, former Arkansas Gov. Mike Huckabee and New Jersey Gov. Chris Christie. However, Carson has huge support among social conservatives and is also the favorite among young GOP primary voters, a survey by Harvard University’s Institute of Politics found. In an email sent from Carson’s exploratory committee, he referenced that study as the “final” message about whether or not to run for president, the International Business Times reported.

“I hope that you’ll closely watch your inbox over the next couple of days so that you’ll be one of the first people to know about my decision,” Carson wrote.

msnbc reporter Jane Timm contributed to this report.