UPDATE: President Barack Obama will head to Massachusetts on Sunday in a last-minute bid to revive the fortunes of Martha Coakley, the Democratic candidate for Ted Kennedy's old Senate seat in a special election that takes place Tuesday.

Republican candidate Scott Brown had a four-point lead over Coakley in a poll published Thursday night. That poll has Democrats spooked because the loss of Kennedy's seat to a Republican could jeopardize the Democrats' health care agenda.

Politico reports:

White House press secretary Robert Gibbs announced the president's decision at today's briefing, and said the campaign stop will take place in Boston.

The White House came to the conclusion that it couldn’t afford to stay out of a race in such a Democratic state where the political and policy consequences are so dramatic. A Coakley defeat would jeopardize the fate of the administration’s signature health care legislation – and would send a new wave of fear for vulnerable Congressional Democrats, some of whom [are] mulling retirement.

Original story follows below

Massachusetts Republican Senate candidate Scott Brown took a four-point lead in the latest local poll published Thursday night, raising the specter of a complete collapse of Democrats' healthcare plans.

Democrats need 60 votes to move the healthcare bill forward in the Senate. If Brown wins, replacing the late Sen. Ted Kennedy in a special election, he has promised to filibuster the Democrats' bill. Brown is running against Massachusetts Attorney General Martha Coakley.

Should Brown emerge victorious, Democrats will likely have to return to the bargaining table with GOP moderates, such as Sen. Olympia Snowe (R-ME) and Sen. Susan Collins (R-ME).

Initially, Coakley had been seen as a shoe-in for the seat, as Massachusetts tends to elect Democrats to Senate posts.