Sen. John McCain (R-Ariz.) on Monday called liberal attacks on centrist Sen. Joe Lieberman (I-Conn.) a "disgrace."

McCain backed his Senate colleague on Twitter:

Joe Lieberman – standing up for his principles on health care is being viciously attacked by the liberal left...what a disgrace!

Lieberman, a centrist who caucuses with the Democrats, has drawn the ire of liberals for his continued opposition to healthcare reform legislation.

With no Republicans indicating support for the bill yet, Senate Majority Leader Harry Reid (D-Nev.) may need all 60 Senate Democratic cacucus members to vote for the bill to break a GOP filibuster.

McCain has been one of the few Republican legislators to openly defend Lieberman, who still caucuses with the Democrats.

Lieberman has objected to a number of central elements in the bill, including the public health insurance option and a proposal to allow people who are age 55 to 64 to buy into Medicare. 

Earlier on Monday, Rep. Joe Sestak (D-Pa.) attacked his Senate primary opponent Sen. Arlen Specter (D-Pa.) for saying last year (when he was a Republican) that the Connecticut senator should switch parties.

Cross-posted to the Twitter Room