Sen. Joe Lieberman (I-Conn.) has no plans to make an endorsement in Massachusetts's special election on Tuesday.

A spokesman for the senator shot down rumors that Lieberman would weigh in on the closely-watched special election, in which Republican Scott Brown is waging a surprisingly tough battle against state Attorney General Martha Coakley (D).

Conservative bloggers had been floating a rumor that Lieberman, a centrist, independent senator who caucuses with Democrats, would endorse Brown.

Those rumors, the spokesman said, are "not true," and no announcement is planned on the race.

Lieberman had been a critic of some elements of the healthcare bill before Congress, and the conservative blogs had said the Connecticut senator would endorse the Republican in neighboring Massachusetts to aid the GOP in their effort to get a 41st vote in the Senate, enough to filibuster that and other bills.

Voters will head to the polls Tuesday to decide the race, which is to permanently fill the seat held by the late Sen. Edward Kennedy (D).

Democrats have launched an "all out" effort to keep the seat, including President Barack Obama's campaign stop there Sunday afternoon.