Good question with no easy answer. Let's look at all three legs :
HOUSE -- will pass easily.
STATES -- 38 needed, 38 have DOMA's, of these I would say 30-35 will vote quickly to ratify. Another handful of states are considering DOMA's. MA & Cali are wildcards of course, even though they have DOMA's; but gut feeling is 38 is easily attainable.
SENATE - Aye, there's the rub. First feeling is that the Amendment will not get past the Dem Obstruction. But, a lot of things come into play that make it possible, though not probable. 85 Sens voted for the DOMA, so on the surface one would think CMA would be a lock, but the Dem Machine is already in full mode against the CMA.
Still some will vote Aye -- Zell Miller definately. Any Sen up for Reelection will be pressured greatly to vote Aye (dependent on states of course). There are others who also will be in the position of committing political suicide if they vote no.
I would guess at first glance that there are 60 that will or HAVE to vote Aye.
Now, The bellwether will be Lil Tommy dASShole himself. he is in a campaign for his life in SD against John Thune. Voting Aye will not go over very well in SD, but Tommy is also Sen Minority Leader and as such it is his job to gen up opposition to this. So, he is the initial key --if he says NO knowing that he will kill his reelection chances, then the die is cast and the Dems will be Obstructionists.
All in All this is a WIN/WIN for Pubbies. Kerry has already said NO! He just locked up the Dem base and won the nomination, and he just LOST the General Election. Now, the rest of the Dems have to choose do we toe the party line and let this be a huge wedge issue, or do we save ourselves.