(Click here to follow all the latest developments via Jonathan Cohn's Twitter feed.)

John Larson, chairman of the House Democratic Caucus, told ABC News' Jonathan Karl on Sunday morning that 216 of his members have committed to vote "yes" on the Senate's health care bill.

NBC reported early in the afternoon that Michigan's Bart Stupak, who led a group of Democrats threatening to oppose reform over abortion rights, has agreed to support it.

And while House Democratic leaders have been warning that final commitments are not nailed down--indeed, CNN has since reported that Stupak has not yet affirmed his support--multiple sources tell TNR that the Democrats are likely to have 216 votes tonight.

Keep in mind that even formal whip counts can predict final vote tallies inaccurately. People change their minds, back out of deals, or surprise their colleagues by leaving for Florida. In other words, you don't really have the votes until the votes have been cast.

But if 216 Democrats really do say "aye," that would be enough to pass the Senate bill, readying it for presidential signature and enactment. Health care reform would become law of the land, while amendments to the bill would go to the Senate for consideration there.

The clincher in the House would be be a deal on abortion rights, negotiated over the last few days and late into Saturday night. Under the agreement, President Obama would issue an executive order applying the Hyde amendment to the new insurance exchanges.

As you know, Stupak and his supporters were threatening to vote "no" because they believed reform might allow federal funds to finance abortion services. The Hyde amendment, in place since the 1970s, prohibits that.

Applying it to the exchanges is apparently enough to convince some of those wavering Democrats--including Stupak, who is telling reporters he thinks such a deal could work, and Ohio Rep. Marcy Kaptur, who just announced her intent to vote "yes."

Leaders of the pro-choice caucus in Congress, who had been threatening to oppose reform over concessions to Stupak, have said they can support this deal because it merely reaffirms existing law.