The heat is happening behind closed doors as the U.S. House prepares for a Saturday showdown vote on health care. Access is everything. By keeping Members of Congress in Washington, D.C., this weekend, Democratic leaders keep them away from angry constituents back in their home states, where the Members normally would depart from Friday to Monday. (Note: The tactics aren’t different from what Republicans sometimes used when they held the majority.)

The first step is to keep Congress in town. The second is to keep them monitored and available for whenever leaders want to summons them for backroom meetings—sometimes to discuss and sometimes to pressure and browbeat and offer deals. A “buddy system” is sometimes assigned so a fellow Congressman from the party’s whip team keeps tab on each undecided member’s whereabouts, their cell and other private phone numbers, the places they tend to hangout between votes, and similar information.

Members don’t like to be found and pressured. As one speaker noted at Thursday’s “House Call” tea party event at the U.S. Capitol: “There may be some members hiding right now. They may be in the basement. They may be in the cafeteria, pretending they’re not a Congressman.”

So special gatherings are created, not only to communicate but also to attract the reluctant to join their party’s herd. Then they can be culled out by party leaders for individual attention, much as a sheepdog picks out individual sheep from a flock.

That’s one benefit of scheduling a group meeting with President Obama, as party leaders have set for Saturday. It’s also a reason for scheduling other votes on the House floor, to flush individuals out of hiding and work them over. It’s common for members to rush into the chamber, cast a vote, and try to rush out before they’re caught. So multiple votes are scheduled.

It’s all part of the behind-the-scenes effort to whip crucial votes. It’s not unique to the health care vote. But it’s part of Congress that most people never see. Speaker Nancy Pelosi is taking a big risk with her self-imposed Saturday deadline. Her party has 258 House seats; she only needs 218 of them to support her.

For months she told the media she had the votes. Recent events demonstrate that she didn’t then and still doesn’t now. Pelosi therefore emboldens internal Democrat opposition if she cannot deliver. There’s already talk that Saturday’s deadline will be missed. The problem getting her own party’s approval exposes significant rifts among Democrats. Once Pelosi expends energy on this all-out effort, many within her own party might deny her a second chance if she cannot win this weekend.

Ernest Istook served 14 years as a U.S. Congressman, and is now a distinguished fellow at The Heritage Foundation