Terry McAuliffe, the former governor of Virginia, on Wednesday entered the contest for his old job, simultaneously offering himself as both a trusted steward during an economic and public health crisis and someone prepared to fight against “the old way of doing things.”

“I am running for governor again to think big and to be bold and to take the Commonwealth of Virginia to the next level and to lift up all Virginians,” Mr. McAuliffe said in a brief speech outside a public school in Richmond, the state capital.

Mr. McAuliffe, 63, formally began his campaign surrounded by four senior elected officials, all of whom are Black. The setup was a nod both to the relationships he nurtured during his governorship from 2014 to 2018 and the complex nature of the state’s 2021 primary, in which three Black candidates have already announced their candidacies for the Democratic nomination.

Mr. McAuliffe’s 2021 campaign has for months been an open secret in Virginia — at a March campaign rally, Joseph R. Biden Jr. called him “the once and future governor” — and Mr. McAuliffe’s allies have made the case that his coalition would look a lot like Mr. Biden’s, with core support from Black voters and suburbanites who sent Mr. Biden to the White House.

“We need him to lift the Black community from the crippling pandemic, because he knows that it has hit the Black communities, Black communities and brown communities harder than anyone else,” L. Louise Lucas, the Virginia State Senate president, said while introducing Mr. McAuliffe on Wednesday. “We need his experience and tested leadership, tested leadership, tested leadership.”

Virginia’s contest for governor will serve as a first test of the post-Trump Democratic coalition. For four years, culminating with the 2020 Democratic presidential primary, the party’s voters prioritized electability, choosing more moderate candidates who faced liberal firebrands in nearly all competitive races.

Mr. McAuliffe is the fourth Democrat to enter the 2021 race for governor, joining three Black candidates who have been campaigning for months: Jennifer McClellan, a state senator; Jennifer Carroll Foy, who on Tuesday resigned her seat in the House of Delegates to campaign for governor full time; and Lt. Gov. Justin Fairfax.

But unlike in the presidential contest, in which Mr. Biden sold his electability against President Trump, whichever Democrat emerges from Virginia’s June primary will be a heavy favorite against the Republican challenger.

Virginia has become increasingly Democratic since 2009, the last time Republicans won a statewide office. The party won control of the state legislature in 2019, and Mr. Biden carried the state by 10 percentage points last month.

The Republican field already appears fractured, with Amanda Chase, a Republican state senator who models herself after Mr. Trump, announcing last weekend that she would run as an independent candidate rather than seek the Republican Party’s nomination at a state convention next year. Kirk Cox, a former speaker of the House of Delegates, is seeking the Republican nomination and Pete Snyder, a wealthy marketing executive, may also join the G.O.P. primary race soon.

At the same time some Virginia liberals have pronounced themselves eager to elect Ms. McClellan or Ms. Carroll Foy, either of whom would be the nation’s first Black woman governor. Virginia has never elected a woman to be governor and has not elected a woman to statewide office since 1989.

Ms. Carroll Foy, at 39 the youngest candidate in the field, was not shy about attacking Mr. McAuliffe as a creature of the past.

“Career politicians like Terry McAuliffe are interested in maintaining the status quo,” she said in a statement Tuesday night. “But Virginians are calling for change. They want someone who understands their problems as I do because I’ve lived them. While I respect Terry McAuliffe’s service, he doesn’t understand the problems Virginians face. A former political party boss and multimillionaire, Terry McAuliffe is simply out of touch with everyday Virginians.”

Ms. McClellan, while not attacking Mr. McAuliffe directly, cited her own “life experience” as evidence she would be the best governor in the field in a statement released Wednesday.

Mr. McAuliffe said Wednesday that he would center his campaign on helping the state’s economy recover from the effects of the coronavirus pandemic, pledging Virginia’s largest investment in public education and appealing to Black voters in the Democratic primary in June.

He also leaned heavily on his past tenure as governor, citing fights with Republicans who at the time controlled Virginia’s General Assembly. In the same breath, Mr. McAuliffe promoted his record as governor and called for a new approach to running the state government.

“The old Richmond approach just doesn’t work anymore,” he said. “Folks, it is time for a new Virginia way. I know that old way of thinking because I fought against it constantly as governor, time and time again.”

Mr. McAuliffe is a longtime fixture in Democratic politics, both nationally and in Virginia. He is close enough to former President Bill Clinton that the two men speak daily, and he claims to make more than 100 phone calls every day. A former chairman of the Democratic National Committee, Mr. McAuliffe has run for Virginia governor twice, losing a bitter 2009 primary before winning in 2013. He also weighed a 2020 presidential campaign but bowed out in April 2019 once it became clear that Mr. Biden would seek the Democratic Party’s nomination.

He spent the rest of 2019 campaigning and fund-raising for Democrats running for Virginia state legislative seats, helping the party seize control of both the State Senate and House of Delegates for the first time in a generation.

Virginia’s current governor, Ralph Northam, a Democrat, is forbidden by state law from seeking a second consecutive term. Mr. McAuliffe is vying to be the second Virginia governor since the Civil War to be elected twice, following Mills Godwin Jr., who was elected as a Democrat in 1965 and as a Republican in 1973.

Virginia’s contests for governor, coming the year after presidential elections, have for decades been considered an opportunity for the party that just lost the White House to take control of a large state government. Mr. McAuliffe’s 2013 victory over the Republican Ken Cuccinelli is the only time since Mr. Godwin’s 1973 election that the party that held the presidency also won the Virginia governor’s mansion.