WASHINGTON, DC (AFP) — Former US Secretary of State Hillary Clinton looks set to officially launch her 2016 presidential bid this weekend — a long-anticipated second run at the White House.

The announcement — expected to come tomorrow, according to reports citing sources in her campaign team — would make the 67-year-old the clear Democratic frontrunner in the race to succeed Barack Obama.

The former first lady is expected to announce her candidacy via social media and a video message, several US media reported, followed by a low-key campaign swing through key state Iowa.

Iowa is the first state to vote in the primary season that starts in early 2016. The election is set for November 2016.

Spokespeople for Clinton and the Ready for Hillary organisation did not comment.

Unlike when she first ran for president in 2008, Clinton’s path to clinching the Democratic nomination appears relatively clear.

The wife of former President Bill Clinton leads opinion polls among Democrats, some 60 per cent of whom say they would vote for her in the primaries, according to the website RealClearPolitics.

Two other potential candidates — Senator Elizabeth Warren and Vice-President Joe Biden — have not yet said they intend to run.

On the Republican side, Senators Rand Paul and Ted Cruz have already thrown their hats into the ring, with more candidates likely to follow — including Jeb Bush, former governor of Florida, brother to president George W Bush and son of president George Bush.

Though Clinton has not yet officially announced her candidacy, her supporters and campaign teams have, for years, been preparing the ground for an eventual run.

The Ready for Hillary group has raised more than US$14 million to support her from 135,000 donors. Clinton can also draw on a database of 3.6 million supporters.

She is expected to lead — at least at the start — a low-key campaign, with small events for voters in key states.

“I think it’s important, and Hillary does too, that she go out there as if she’s never run for anything before and establish her connection with the voters,” Bill Clinton told Town and Country magazine.

“My role should primarily be as a backstage adviser to her until we get much, much closer to the election.”

A humble approach may help dispel doubts about Clinton raised in recent weeks, after it was revealed that she used a private e-mail address when she was secretary of state from 2009 to 2013.

Detailed examinations of donations from foreign states and businesses to the Clinton Foundation when she was secretary of state have also raised questions about potential conflicts of interest.

After months of preparation, Clinton seems likely to have drawn valuable lessons from her 2008 defeat in the Democratic primaries to Obama.

She has used hashtags like GrandmothersKnowBest and YouGoGirl in her tweets to take jabs at Republicans in Congress and encourage young girls to pursue careers in IT.

Clinton has also talked about her new role as a grandmother to daughter Chelsea’s own daughter, Charlotte — a stark contrast to the tough-as-nails image she cultivated in 2008.

For Lara Brown, the director of the graduate programme in political management at George Washington University, Clinton — who would be the first female US president if elected — will surely reposition herself this time around.

“In 2008 she attempted to position herself essentially as Margaret Thatcher, as somebody who was strong, but not necessarily somebody who consciously focused on or related to her gender as a political advantage,” Brown told AFP.

“I think certainly she and her campaign team learned from 2008 that there is power in being a first.”

Brown said Clinton needed to ensure that as many Democratic women as possible, especially young women, cast their ballots — a strategy Obama used in the African-American community.

Jennifer Lawless, director of the Women and Politics Institute at American University in Washington, said Clinton was working on softening her image.

“People believed that she was confident, and that she was a strong leader. They were less inclined to think of her as very empathetic or particularly likeable,” Lawless said.

“The grandmother hashtag is one perfect example of how she’s beginning to address that.”

More so than in 2008, Clinton’s strength on foreign policy will be an asset, but if her recent tweets indicate anything, it is that she will focus on the economy, the middle class, wage inequality and social issues.

She will need to both set herself apart from Obama, and reassure the left wing of the party, which has criticised her ties with Wall Street.

Clinton has often touted the use of data in her decision-making. She will promote an evidence-based approach to governing.

“You have to do the research, you have to run the numbers. That’s how we minimise risk and maximise impact,” she said in December.