· House passes the Senate version as-is.Right now the healthcare bill is in conference, meaning the House and Senate are coming up with a compromise that bouth bodies could then go back and pass. But if Democrats fell below the 60 vote threshold, it's possible that house Democrats could drop all compromise demands, and simply vote in favor of the Senate bill, which would then not require a second vote in the Senate. This seems unlikely though, given that there are differences between the two, and since a Martha Coakley loss would cause a lot of moderate Dems to get nervous.
· Democrats succeed in slowing the seating of Scott brown, giving the 60 sitting members time to vote. If Scott Brown wins, expect all kinds of legal challenges, recounts, and other efforts to slow his seating, giving Congress time to pass the bill. This would look horrible to voters, and it may not even work given the amount of time required to reach a compromise.
· Democrats succeed in slowing the seating of Scott Brown, but Republicans succeed in preventing sitting Senator Paul Kirk from voting. Democrats might be able to slow Brown's entry into the Senate, but Republicans are already taking about their own trick. In The Weekly Standard, conservative commenter Fred Barnes argues that under Massachusetts law, sitting senator Paul Kirk is ineligible to vote right after the election takes place, regardless of who wins.
· Democrats bend Senate rules in order for healthcare to pass with 51 votes. Apparently Democrats could, theoretically, break Senate rules in such a way that would allow the Senate to pass healthcare reform with only 51 votes. We haven't seen a clear explanation of how this would work, though it might require the bill to be scaled back in some way.
· Democrats convince a liberal GOP Senator (like Susan Collins) to support healthcare reform.There are one or two Republicans who might be willing to support a bill, though we haven't seen this proposed too seriously.
· Healthcare dies. Probably the most likely scenario. See Megan McArdle's explanation here.