The dust has settled from a historic week in Massachusetts politics. And as we start a new week, Secretary of State John Kerry and his successor William "Mo" Cowan begin their new jobs in Washington. But in less than three months, Massachusetts will hold a primary, which is a step toward electing a new U.S. Senator.

It’s on:

“My name is Ed Markey and I am running for the United States Senate,” U.S. Rep Ed Markey formally announced on Saturday.

The 19-term Democrat from Malden raced through Springfield on Saturday, telling anyone within earshot why Western Massachusetts was critical to his campaign.

“Western Mass. is going to be key to winning this election and I am going to be out here over and over again,” Markey said.

Stephen Lynch kicked off his campaign days earlier with a professional web video designed to introduce himself to voters statewide.

“He began in public housing,” the ad says. “His mother was a postal clerk, his father an iron worker.”

And Lynch said biography is a key difference between him and Markey.

“Well, It’s certainly one of perspective in who we are as people,” Lynch said. “I grew up in the Old Colony Housing Projects. I know what it is to struggle. My family struggled early on. I worked as an ironworker early on. I know what its like to live paycheck to paycheck.”

But in this battle of dueling biographies, Markey is quick to point out that his father was a milkman. Both Congressmen support traditional Democratic policies on Social Security and Medicare. But on other key issues they are a study in contrasts. Markey is a strong supporter of reproductive and abortion rights. Lynch, a South Boston Catholic, opposes abortion, though he says he would not seek to impose his personal views on women. And I pressed Markey to explain other differences:

Phillip Martin: How do you contrast yourself with Congressman Stephen Lynch?

Ed Markey: I’m going to run a positive campaign on the issues I think are most important, and that is gun control, and the creation of jobs, climate change and the rights of women and gays and lesbians in our society.

Lynch also supports these issues to various degrees, though when he served in the state legislature he opposed partner benefits for gays and called efforts to ban assault weapons “feel-good legislation.” But in the wake of the Newtown, Conn., murders of schoolchildren and teachers, Lynch now says he "fully supports President Obama's reasonable gun control recommendations.”

Markey, meanwhile, went a step further over the weekend. He called on Congress to approve tough new gun laws and to be willing to go against the National Rifle Association.

“The NRA used to stand for National Rifle Association,” Markey said. “The NRA today stands for ‘not relevant anymore.’ And we have to make sure that we mount the campaign and put the strong gun laws on the books.” 

There is not much daylight between Markey and Lynch on gun control measures, but on other issues there is further contrast. For example, Markey supported the TARP bailout of Wall Street. Lynch proudly opposed it.

“One of just two Massachusetts representatives to vote against the $700 billion Wall Street bailout, because it did everything for Wall Street and nothing for the people they hurt,” his announcement ad says.

Lynch’s willingness to go against his party, and his humble beginnings, have some comparing him favorably to Scott Brown and his famous pickup-truck persona.

“I don’t think our backgrounds are that common,” Lynch said. “Scott brown did have a pickup truck and I had a pickup truck. I had a different type of truck. Mine was a work truck. I didn’t drive from my law office to my apartment. I actually went to work everyday. And I know what it’s like to stand in an unemployment line and I would not have voted against extension of unemployment benefits. And so I think we’re greatly different and I don’t know what this means now that he’s out of the race.”

It could mean that Lynch still stands to benefit from some of Scott Brown’s more conservative Democratic supporters. This includes fellow lifelong residents of South Boston, most notably former Boston mayor Ray Flynn. This is what Flynn told me a few months ago based on the possibility that Lynch might run for the U.S. Senate.

“Put it this way, I can’t answer that question that hypothetical until it happens,” Flynn said. “But every election that Stephen Lynch has ever ran, I’ve supported him.”

Meanwhile, Ed Markey is hoping to draw on the same coalition of voters that elected Elizabeth Warren to the U.S. Senate: Democrats of all stripes -- liberals, minorities …

“… Women and gays and lesbians,” Markey said.

Markey also has the support of the Democratic establishment both in and out of the state. He’s been endorsed by John Kerry, and by Vicki Kennedy, the widow of the late Sen. Ted Kennedy.

Lynch has acknowledged his underdog status. Prior to entering the race he observed that the Democratic Senate Committee has about $40 million to spend, and that Markey is their standard bearer. But he said that would not stop him from running in this election.