House Speaker Paul Ryan still appears to be short of the votes he needs to pass the American Health Care Act, but he's been picking off a few wavering moderates and conservatives here and there as the vote — scheduled for Thursday — draws nearer.

Will it be enough? I don't know, and neither does Ryan.

So rather than trying to predict the future, let's look to the past for some scenarios about how big votes like this one tend to play out. Four come to mind.

1) The Pelosi scenario: In the first two years of the Obama presidency, big dramatic votes in the Democrat-controlled House tended to go down in the same basic way.

In the days before the vote, there would be drama, and the bill's chances of passing would appear uncertain. But Speaker Nancy Pelosi would work wavering members, calling in favors from some and making policy concessions to others.

In the end, the bill would get ju-u-u-ust enough votes to get through. This pattern played out twice for Obamacare (there were major votes on it in both 2009 and 2010), for Dodd-Frank, and for the climate bill (which then died in the Senate).

This is obviously what Ryan is trying to make happen, and the similarity here is that Republican members will feel pressure not to tank the new president's priorities. (They might also recall, of course, how the Pelosi strategy of passing big controversial bills was followed by Republicans' 2010 midterm landslide.)

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A key difference here is that Pelosi's concessions were mainly aimed at winning over moderate Democrats, with almost all staunch liberals already on board. She didn't have to negotiate with an ideological bloc. Which brings us to...

2) The Boehner scenario: Since Republicans took the House under President Obama, a different scenario has tended to play out on high-profile votes.

Republican leaders would keep professing optimism that the bill would pass ... until shortly before the scheduled vote, when it became clear they didn't have enough support from their own party (often because of opposition from the right).

Rather than face a humiliating defeat on the floor, GOP leaders would usually postpone the vote — sometimes indefinitely. Depending on the particular issue, they would either try to rework the bill to get more support or abandon it entirely.

This is what many in the House Freedom Caucus are hoping will happen this time. They feel they've been ignored by Speaker Ryan, who has crafted a bill that retains too much of Obamacare. They want to show they can't be taken for granted.

The difference here, though, is that Donald Trump is president, not Barack Obama, and Trump wants this bill to pass. The president is very popular in many Freedom Caucus members' districts, so perhaps enough of them would end up shying away from dealing him such an embarrassing defeat.

3) The DeLay scenario: What happens when House leaders bring a bill to the floor despite not having the votes?

Then-House Majority Leader Tom DeLay (R-TX) showed one possibility in 2003. That year, he brought Medicare Part D to the floor despite not having the votes in hand ... and when the initial tally came in, there were more "no" votes than "yes" votes.

But DeLay refused to take no for an answer. Instead, he held the vote open for several hours after the allotted time expired, so he could cajole or pressure Republicans to change their minds. Eventually he got his way, and closed off the vote at 5:53 am after enough members flipped.

It later emerged that he'd used some extremely shady tactics — the House Ethics Committee eventually rebuked him for offering to endorse a wavering member's son in a congressional primary should said member switch his vote. But though it was ugly, he did win, and Medicare Part D became the law of the land.

4) The failure scenario: It's extremely unusual for the House majority to bring a high-profile bill to the floor, conduct a vote, and lose it. What's more common is for leaders to realize they don't enjoy sufficient support beforehand, and preemptively postpone or cancel the vote as a result.

Still, we should at least mention failure as a possibility. It happened during the 2008 financial crisis, when the TARP bailout bill at first failed to pass the House (though a subsequent market crash helped convince the House to pass a slightly revised version soon afterward). Sometimes the people in charge screw up.

A Senate AHCA vote next week?!?

Back in 2009, Obamacare famously languished in the Senate for months on end. Mitch McConnell has no intention of repeating that experience. The Senate GOP leader said Tuesday that should the House pass the health bill, he expected the Senate to "reach a conclusion" on it next week.

That's ... an astonishingly rapid timetable for a massive and controversial bill that's been trashed by so many members of the Senate so far. Furthermore, most whip counters think the bill will need a major overhaul to have any hope of passing the upper chamber, so that would sure have to happen quickly to meet this deadline.

Of course, though, the "conclusion" the Senate reaches could simply be "no," which would free the body to move on to other things.

Chart of the Day

These Center on Budget and Policy Priorities charts show a serious boon one group would get from the House GOP bill: The AHCA repeals Medicare's additional Hospital Insurance payroll tax and the Medicare tax on unearned income, which only fall on the very wealthy.

Today’s health politics and policy reads

With research help from Caitlin Davis.