Congressmen Stephen Lynch and Ed Markey are officially launching their campaigns this week for US Sen. John Kerry’s seat, and Boston’s elected officials at City Hall and the State House will no doubt find themselves caught in the crossfire.

The shortened timeline of the race – the primary likely will be set for the end of April and the general election is expected to be in June – means Lynch and Markey will be chasing not only consistent voters, but fellow elected officials for their endorsements.

Lynch, a South Boston Democrat and former ironworker, told supporters in an e-mail Tuesday afternoon that he planned to announce his decision today at the Ironworkers Local 7 Hall on Old Colony Avenue. While he has publicly said a “final decision” will be made then, his advisers and allies have been telling reporters for over a month that Lynch is in.

Both Lynch and Markey, a Malden Democrat, attended Mayor Thomas Menino’s State of the City address on Tuesday night in Faneuil Hall. They sat in the same row, separated by Congressman John Tierney (D-Salem), and stood steps away from one another as they were mobbed by reporters looking for the latest updates on their campaigns.

Asked if he has requested an endorsement from Menino, Lynch told reporters, “I’ve sat down with him, yeah, towards that end. We’ve had a couple of meetings. I haven’t sat with him since [Congressman] Mike Capuano got out of the race, though. At that point he had two city of Boston members of Congress that were potentially in the race.”

Lynch, who shares an adviser with Menino in longtime political consultant Ed Jesser, added that it was Menino’s night and that “we’ll talk again.”

Members of the Boston delegation, interviewed over the last few days, were largely coy in their public remarks, with some noting that Lynch had not formally announced his intention to run. Whatever the split in the delegation will be, it’s not likely to be an easily describable one, like progressives versus labor, liberals versus conservatives, or South Boston versus Dorchester.

Lynch is frequently described as the most conservative member of the Bay State’s Congressional delegation, stemming in part from his pro-life stance.

“None of us can define who is too liberal or two conservative for the seat,” said District 7 City Councillor Tito Jackson, who has worked for Gov. Deval Patrick. “The voters will determine who will get into the seat.”

Even so, it’s hard to see left-leaning lawmakers like Jackson, City Councillor At-Large Felix Arroyo, Sonia Chang-Diaz, a Jamaica Plain Democrat who represents parts of Dorchester and Mattapan, and state Rep. Linda Dorcena Forry, a Dorchester Democrat, throwing their support behind Lynch over Markey, a staunch liberal.

Over the last month, Markey has picked up the endorsements of state Treasurer Steve Grossman, Attorney General Martha Coakley, and House Speaker Robert DeLeo (D-Winthrop).

State Rep. Marty Walsh, a progressive Democrat from Savin Hill, will likely back Lynch. Unions figure prominently in both their biographies and they have a long history together. South Boston’s Jack Hart, who lives across the street from Lynch and is leaving the state Senate for a law firm tomorrow, will likely be in the Lynch camp, as will state Rep. Nick Collins, a fellow South Boston Democrat.

State Rep. Russell Holmes, a Mattapan Democrat, said he is leaning toward supporting Lynch, calling him a “friend” who gave him advice when Holmes first ran for office in 2010. “Stay true to your family and stay true to the Lord,” Holmes recalled Lynch saying.

For his part, Lynch remained cagey about whether he’s fully in, despite sources telling reporters last Friday that was exactly the case.

Even as he headed into the Dorchester offices of SEIU 1199 that day, Lynch told the Reporter he hadn’t made a final decision. “One of the news outlets said I had announced, and I had a date and I had an event planned and all this stuff, and that was totally premature. We’re still – obviously I’m here to talk with the SEIU, I just left the plumbers’ union hall,” he said. “I’ve got some people that I’ve got to talk to up in Lowell and Haverhill tomorrow. So we’re still, we’re still, you know, doing the outreach that we need to do to measure our support, to make sure that if we get into this thing, that we can run a good strong campaign.”

In a statement released the same day, state Democratic Party chairman John Walsh said that if a primary occurs, it will showcase a “deep pool” of Democratic talent. “If there is a primary, the Massachusetts Democratic Party will endorse no candidate and we will remain focused on building a grassroots coordinated campaign to support whoever becomes our nominee to keep John Kerry’s ideas and values moving forward,” he said.

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