Former White House spokeswoman Sarah Sanders running for Arkansas governor

Former White House Press Secretary Sarah Huckabee Sanders calls on reporters during a press briefing at the White House February 12, 2018 in Washington. Photo / Getty Images

Sarah Sanders, Donald Trump's former chief spokeswoman and one of his closest aides, is running for Arkansas governor, a source told The Associated Press on Sunday night.

Sanders, who left the White House in 2019 to return to her home state, planned to announce her bid on Monday, a senior campaign official told the AP on condition of anonymity. The campaign official spoke on condition of anonymity because they were not authorised to speak publicly.

A formal announcement is expected Monday.

US President Donald Trump stands with Sarah Huckabee Sanders, after she announced that she is stepping down as the White House press secretary in June 2019. Photo / Getty Images

The former White House press secretary is launching her bid less than a week after the end of Trump's presidency and as the ex-president faces an impeachment trial. But Sanders is also running in a solidly red state where Republicans tend to embrace the former president.

The daughter of former Governor Mike Huckabee, Sanders had been widely expected to run for the office after leaving the White House — and Trump publicly encouraged her to make a go. She's been laying the groundwork for a candidacy, speaking to GOP groups around the state.

Sanders joins an expensive Republican primary that already includes two statewide elected leaders, Lt. Gov. Tim Griffin and Attorney General Leslie Rutledge. The three are running to succeed current Governor Asa Hutchinson, a Republican who is unable to run next year due to term limits.

No Democrats have announced a bid to run for the seat.

Sanders launched her bid weeks after a riot by Trump's supporters at the US Capitol left five people dead. More than 130 people have been charged in the insurrection, which was aimed at halting the certification of President Joe Biden's win over Trump.

Sanders was the first working mother and only the third woman to serve as White House press secretary. But she also faced questions about her credibility during her time as Trump's chief spokesperson.

During her nearly two-year tenure as Trump's chief spokeswoman, daily televised briefings led by the press secretary ended after Sanders repeatedly sparred with reporters who aggressively questioned her about administration policy and the investigation into possible coordination between Trump's campaign and Russia.

But Sanders earned reporters' respect working behind the scenes to develop relationships with the media.

Trump's tumultuous exit from the presidency may do little damage to Sanders in Arkansas. Republicans hold all of Arkansas' statewide and federal seats, as well as a solid majority in both chambers of the Legislature.

Griffin and Rutledge have combined raised more than US$2.8 million in the race, which could get even more crowded. Republican state Sen. Jim Hendren, who is also a nephew of Hutchinson's, is considering a run.

Sanders, who published a book last year and joined Fox News as a contributor after leaving the White House, enters the race with a much higher profile than any of the candidates.

But she remains an unknown on many of the state's biggest issues and has said she doesn't want to distract from Hutchinson's agenda.