Chris Bowers has the news on Tester.
Senator Jon Tester (D-MT) would vote in favor of Senator Schumer's "level playing field" public option.
This pushes the Senate whip count to 51, even without Joe Biden casting a tie-breaking vote.
Since there are now finally 60 active, voting Democrats, it is possible to break any Republican filibuster. Hell, it actually only requires 51 votes to break a filibuster, if Senators were more honest about process. Further, if they didn't even want to both with filibusters, they could always just go with reconciliation, since Tester now gives them enough votes even if Robert Byrd (who is opposed to using reconciliation for health care) defects.
Senate Democrats have the votes. No more process excuses. Pass the public option.
Tester's support is for the weaker Schumer level playing field public option, but its public option support nonetheless. Would he vote against a stronger public option? Highly unlikely.
As Chris says, Reid's got his 51 votes. This can be done two ways, either of which require Reid and Obama forcing the issue on a cloture vote--making Democrats commit to not supporting a Republican filibuster--or doing it through reconciliation.