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The Senate will be working overtime this week to pull together its ObamaCare overhaul measure -- voting on a pile of amendments and procedural matters to get a complete bill on President Trump’s desk as soon as possible.

Essentially all of the work will fall on leaders of the Republican-controlled chamber who must get enough votes for final passage of their measure, after clearing a major hurdle Tuesday of getting enough votes to even begin debate. (No Senate Democrats or independents support the measure.)

Math is always critical on Capitol Hill: Nothing better exemplified that assertion better than the return of Sen. John McCain, R-Ariz., to the Senate on Tuesday afternoon following brain surgery. McCain trekked back across the country to make the procedural vote to launch the debate.

His presence (and yes vote) gave the GOPers 50 yeas on the motion to proceed. Had McCain not been there, the vote likely would have been 49 Republican yeas and 50 noes. That would have killed the health care effort immediately. McCain’s presence produced the tie and allowed Vice President Pence to break the deadlock, 51-50.

The Senate is using a special process for health care bill to sidestep a Democratic filibuster.

Sixty votes are needed to overcome conventional filibusters. Republicans knew they didn’t have the votes for that. So they opted for the special, filibuster-proof gambit. But the problem wasn’t with Democrats. Republicans were barely able to scrape together enough votes from their own side of the aisle just to begin debate on the legislation.

There was no better example of this than when Pence broke the tie on the motion to proceed. Yes. Fifty senators may have voted to start debate. But as McCain predicted in his speech, getting 51 yeas for this bill -- or even 50 so they can again turn to the vice president -- is problematic.

The bill can’t shift too far to the right or left. It’s fragile enough as is. It seems as though the Republican brass may never be able to get Sen. Susan Collins, R-Maine, to vote yea. And whether they can persuade Sen. Lisa Murkowski, R-Alaska, is unclear.

The GOP senators on the right to watch will be Mike Lee of Utah, Rand Paul of Kentucky, and Ted Cruz of Texas.

Those in the middle of the Senate Republican Conference -- whose votes also are no sure thing -- include Sens. McCain, Dean Heller of Nevada, Jeff Flake of Arizona, John Hoeven of North Dakota, Cory Gardner of Colorado, Shelley Moore Capito of West Virginia, Ron Johnson of Wisconsin and Rob Portman of Ohio.

This is the problem House Republicans encountered with the health care bill they passed several months ago. The leaders fixed one problem for the conservatives and simultaneously created another problem with the moderates.

The turning radius is narrower in the Senate than in the House. That’s why the margin for error is virtually nil. It will represent a Herculean effort if Senate Majority Leader Mitch McConnell, R-Ky., holds everyone together and doesn’t lose more than two votes.

In the coming days and expected late nights, all before Congress leaves for its August recess, Americans can expect to hear the senators talk about such procedural matters as “budget reconciliation,” “point of order,” “waive the Budget Act,” and “vote-a-rama.”

Budget reconciliation is the special procedure the Senate is using to debate the health care bill.

The parliamentary procedure or tactic limits amendments and debate (debate, nothing else) to 20 hours.

The advantage of such a procedure is that it turns off filibusters -- provided the Democrats or Republicans who control the chamber are united.

Points of order are grievances senators may lodge against a bill if they don’t feel the Senate is operating within the rules or strictures of budget reconciliation.

However, the Senate can vote to “waive the Budget Act” (which created the budget reconciliation process in 1974) with 60 yeas.

The Senate already ran into this problem Tuesday night, after the successful procedural vote.

Sen. Patty Murray, D-Wash., made a point of order against an amendment written by Cruz to pare down coverage plans/requirements.

The Senate then attempted to overcome Murray’s point of order and waive the Budget Act. But the Senate fell short of 60 yeas. That vote alone to exclude the Cruz amendment casts doubt on the potential for success with the health care bill.

Vote-a-rama is when the Senate votes on all amendments and points of order in a tranche. The Senate may vote for hours on end, just one roll call tally after another.

A final vote on the bill is expected late Thursday or midnight Friday.

What about the House if the Senate approves a health care bill?

McConnell has delayed the start of the August recess by two weeks. But Fox News is told there is no plan to keep the House here past Friday, the scheduled start of the recess.

A senior House leadership aide tells Fox it will evaluate what the Senate approves (if senators can in fact pass something) and determine whether the House needs to come back in August.

House Majority Leader Kevin McCarthy, R-Calif., told members he reserves the right to recall lawmakers within a 72-hour period.

Also, if the House and Senate adopt different versions of health care, it may take weeks or months to resolve the differences.

The House passed the original version of ObamaCare in November 2009.

The Senate approved its version a month later. The House and Senate then took until late March 2010 to merge the bills and send a final, unified product to then-President Barack Obama’s desk.

Just the required reading all of the amendment will take time. At 5:52 p.m. Tuesday, a Senate clerk began reading out loud all 178 pages of the GOP’s health care plan from the dais in the chamber. Four reading clerks rotated in this exercise until 8:23 p.m.

In fact, three readings are required before a vote.

The custom dates back to when there was often only one copy of a bill.

Bills were “read” out loud in the chamber so all members understood the issue at hand. In the 18th and 19th Centuries, some members relied on “hearing” the bill read aloud … because they were illiterate.

The so-called readings of bills and amendments rarely go on for more than a few sentences before someone asks that the reading end.

But if someone in the Senate objects, the reading must continue. That’s exactly what happened late Tuesday afternoon. Democrats objected to suspending the reading. The reading eats up inordinate amounts of time and is a dilatory tactic.

At 8:23 p.m., Senate Budget Committee Chairman Mike Enzi, R-Wyo., asked unanimous consent that the clerks cease the reading. Nobody objected even though the clerks were only about three-quarters of the way through the bill.

Capitol Attitude is a weekly column written by members of the Fox News Capitol Hill team. Their articles take you inside the halls of Congress, and cover the spectrum of policy issues being introduced, debated and voted on there.