What has Kevin McCarthy given up, and at what price?

The fourth day of voting for Speaker of the House has left Kevin McCarthy on the brink of victory. Of the 20 Republicans who opposed him, only six remain.

Getting the rebels to switch, however, was not an easy job. Mr McCarthy has had to make promises, and key concessions, that limit his own power and increase the influence of conservatives in the House of Representatives.

What has he given up - and at what price? Every concession Mr McCarthy makes comes with a cost. Although an agreement has not been publicly announced, here's a look at some of the reported pieces in play.

One of the key demands of the Republican holdouts was the ability for just one legislator to trigger a vote on whether to remove the Speaker from office. This "motion to vacate" could spawn another round of voting in the House, just like what we've seen this past week, serving as a proverbial sword dangling over his head for every minute he has the gavel.

Cost: The motion to vacate is a rule that has a long history in the Congress, but the number of people necessary to trigger it was raised to five in recent years to prevent a lone member of Congress from threatening the Speaker's power. While the holdouts have promised not to abuse the privilege if it is restored, Mr McCarthy's hold on power will be much more unstable with it in place.

Students of US civics - and fans of the old children's TV series Schoolhouse Rock! - may recall learning about how bills work their way through the House of Representatives. They're introduced by a legislator, assigned to a committee for review and revision, brought to the floor of Congress and further amended, then given an up-or-down vote.

That is not how things work very often these days, as massive spending bills are negotiated behind closed doors and passed on short notice and with little debate. Mr McCarthy promised to make bill-passing more like the good old days, with members of Congress outside of the top leadership having more say over how bills are proposed, amended and passed.

Cost: The reason regular order has mostly ended is that legislating, particularly with modern partisan divisions, is hard. Crafting new bills is an arduous task and the process can easily be torpedoed by a handful of politicians with an agenda. While returning to the traditional rules of the game is a noble cause, it is going to be a hard promise for Mr McCarthy to keep.

As its name might suggest, the House Rules Committee essentially sets the rules of the game on the floor of the House. The committee determines when a bill will be voted on, how long it is debated for and how it can be altered by amendment on the floor - or whether it can be changed at all. Mr McCarthy has guaranteed to give the hard-core conservatives at least one seat on this powerful group.

Cost: A seat at the table gets you in the game. With more representation on the Rules Committee, conservatives will be able to shape the kind of legislation the House produces before it fully takes shape - and nip undesired proposals in the bud.

Several of the holdouts have had their eyes on the gavels in influential House committees. Andy Harris of Maryland, for instance, has expressed an interest in chairing the health subcommittee of the House Appropriations committee, which controls billions of dollars in government spending. Mr Harris switched his support to Mr McCarthy on Friday afternoon. Mr McCarthy has made no public promises, but legislators will be watching closely to see if any Republicans get rewarded for their intransigence.

Cost: Giving a committee chair to a holdout means taking it away from a loyal McCarthy supporter who should have been next in line based on seniority. Mr McCarthy may end up making some enemies within his own camp if he promises too much to his former opponents.

A common complaint among hard-core conservatives has been that federal spending has surged to unsustainable levels. During the Speaker fight, they have asked Mr McCarthy to commit to tangible fiscal restraints, such as cutting spending to 2022 levels, requiring that any increase in the amount of debt the government issues be tied to corresponding budget cuts, and allowing individual lines of spending to be removed from larger legislation through votes on the House floor.

Cost: With majority control of the House, Republicans will be able to pass any budget levels they agree on. Mr McCarthy is committing himself to siding with budget hawks in these intra-party debates - which has already angered some conservatives who fear massive cuts to defence spending. Republicans in the House will eventually have to negotiate with Democrats in the Senate to pass spending legislation, however. Mr McCarthy's commitments here could give him less room to work out the kind of compromises necessary to avoid a government shutdown later in the year.

The issue of congressional term limits and border security have been frequent topics of conversation among the Republican holdouts. Mr McCarthy has reportedly promised to hold votes on both early in the year.

Cost: The House was certainly going to take up the immigration issue quickly no matter what the holdouts wanted, as tightening border security and immigration policy have been the centrepiece of the Republican agenda since the start of Donald Trump's presidential campaign in 2015. As for term limits, such a reform would probably require a constitutional amendment to enact. The Supreme Court has already ruled that state attempts to restrict the terms of members of Congress is unconstitutional.