State Sen. Dan Wolf, an airline executive who has carved out a reputation as a liberal reformer, has formally declared his candidacy for governor.

"With your encouragement and support, with an entrepreneurial spirit and love for our great commonwealth, I'm excited to announce my candidacy to be your next governor," he said, in a Web video released Wednesday morning.

Wolf enters what is expected to be a crowded field on the Democratic side, with Gov. Deval Patrick set to step down after two terms.

Treasurer Steven Grossman has indicated that he will declare at the state Democratic convention this weekend. And Attorney General Martha Coakley and U.S. Rep. Michael Capuano are weighing candidacies.

A Capuano spokeswoman says he will not declare his intentions either way at the convention.

Somerville Mayor Joseph Curtatone has suggested he will run if Capuano, a former Somerville mayor, does not. And Boston Globe columnist and national security expert Juliette Kayyem is also considering a run.

Former Obama administration health care official Donald Berwick of Newton and former Wellesley selectman Joseph Avellone have already declared.

The declared candidates — Berwick, Avellone and Wolf — will all speak at the state Democratic convention Saturday.

Coakley and Grossman will have smaller speaking roles in their capacities as statewide elected officials.

Wolf, a Pennsylvania native, spent summers on Cape Cod as a child. A graduate of Wesleyan University, he managed Chatham Municipal Airport and worked as a flight instructor before co-founding Cape Air.

Wolf, who serves as CEO of the company, told WBUR his campaign will place a heavy emphasis on his private sector experience — emphasizing his job creation bona fides and push to create a "business with a conscious."

Cape Air is the only airline in the country with a woman president. And half the management team are women.

The company has offered employees paid sick leave for years. And Wolf has been a vocal advocate, this year, for long-sought legislation that would require employers statewide to do the same.

"This for me is taking what I thought I was able to accomplish at Cape Air, which is to really provide a great workplace and jobs with dignity and build a great company — really expanding that out to help the middle class that has been so challenged over the last number of years," he said.

Wolf, first elected to the state Senate in 2010, has emerged as a liberal voice in the Legislature in recent years — trumpeting the cause of universal health care and pushing for a hike in the minimum wage.

In February, he took a shot at likely gubernatorial rival Grossman when the treasurer voiced doubts about Patrick's ambitious push for a $1.9 billion tax hike to fund large-scale investments in transportation and education.

"It’s time to have an honest conversation about investing in a healthy economy, healthy communities — and by the way, what it means to be a Democrat," he said, in a statement.

The Legislature has since rejected Patrick's proposal in favor of a smaller tax-and-spend package, deeming the governor's approach too aggressive amid a modest economic recovery.

Wolf's reputation as a progressive outsider puts him in line with figures like Patrick and U.S. Sen. Elizabeth Warren, who have had success in Massachusetts politics in recent years. And he invoked both figures near the close of his announcement video.

But Wolf, who represents a relatively conservative part of the state, played down any suggestion that he would run as the liberal candidate in the race — positioning himself as a job creator of broad appeal.

Still, his early message has a populist tinge to it. "Our great wealth — our common wealth — has been concentrated in the hands of fewer people," he said, in the Web video, "literally at the expense of our middle class and working neighbors who built this country."

He said, in an interview with WBUR, that his push to shrink income inequality would begin with a push for high quality early education and a more affordable higher education system.

Building the new energy economy and a more robust transportation infrastructure will be important elements too, he said.

Wolf is not a well-known figure, statewide. And he would face a significant name recognition gap if he goes up against figures like Coakley or Capuano. But he said he likes the role of underdog.

Charlie Baker, the Republican gubernatorial nominee in the 2010 race, is expected to mount another campaign next year. Former U.S. Sen. Scott Brown is another possible GOP candidate.

Fred Thys contributed to this report.