So, now what? Relieved Democrats may still be celebrating the passage of landmark health care overhaul legislation, but Republicans in the Senate still have an opportunity to try to derail the bill. And if history is any guide, they are likely to force the House to vote on health care again before Easter. "Anybody that thinks that this is only going to be a one-time deal today in the House, I think, is grossly mistaken," said Republican Sen. Orrin Hatch on CNN's "State of the Union." Late Sunday, the House passed the Senate's version of the comprehensive bill, and because most members didn't like it, they also passed a smaller bill of so-called "fixes." Passing of those subsequent fixes was a critical component to passage of the Senate bill for House Democrats. Without them, House Democrats would have been supporting a bill with elements deemed largely undesirable. A promise by Senate Majority Leader Harry Reid that the Senate would work to approve the package of fixes coaxed "yes" votes from many Democratic lawmakers who had previously indicated they might oppose the Senate bill. On Tuesday, the Senate is expected to formally start its work on the fixes bill using a little-understood procedure known as reconciliation. For Democrats, reconciliation is the perfect antidote to what they feel is Republican obstructionism in the upper chamber. The process is filibuster-proof, requiring only 51 votes for final passage rather than the usual 60 to overcome a blockade by the minority party. For Republicans, reconciliation is their best chance to kill the smaller bill or make changes to it. Because the House and Senate must pass the same bills word for word even a minor tweak would send it back to the House for another vote. Republicans hope to force major changes to the reconciliation bill, some that could set up a political nightmare scenario for Democrats. If certain unpopular provisions of the Senates version of the bill like special carve-out deals for individual states are not corrected, Democrats risk being branded as supporters of back-room deals. And if Republicans manage to scuttle reconciliation language that would delay the implementation of new taxes on high-value insurance plans, union groups who were counting on the fix will be incensed. In the 22 times that reconciliation has been used, only once has the Senate bill not been changed and sent back to the House. Reconciliation's basic rules Reconciliation is a fast-track legislative process specifically designed to reduce deficits. Debate is limited to 20 hours, but an unlimited amount of amendments can be offered and voted upon. Every line in a reconciliation bill must adhere to strict rules to ensure a budgetary impact or else risk being eliminated by the non-partisan Senate parliamentarian. Here lies the biggest opportunity for the GOP. Cutting up the billTo ensure that all provisions of the bill have a budgetary impact, the rules of reconciliation allow Republicans to raise 19 different types of objections. The most commonly used objection (also called a "point of order") is known as the Byrd Rule, named after its author, West Virginia Sen. Robert Byrd. This can be raised against any part of the reconciliation bill that does not address budgetary matters. The extraneous matter would be removed from the bill if the parliamentarian, Alan Frumin, upholds that point of order. "House Speaker Nancy Pelosi's reconciliation fixes could easily be blown to pieces in the Senate," Sen. John McCain, R-Ariz., said on the Senate floor last week. Reid can ask for a vote to overrule the parliamentarian, but it would take 60 "yes" votes in most cases. With the election of Massachusetts Republican Scott Brown in January, Democrats only have 59 votes in their caucus. There are also other rarely used points of order which could be used to effectively kill the entire bill.