Senate Majority Leader Mitch McConnell is hoping to close out 2018 with a bang and silence the skeptics who just a few short months ago were ramping up calls for his ouster following a brutal defeat on the Republican effort to overturn the 2010 health care law.

But after creating an intricate web of promises to get the GOP tax legislation past the Senate, the Kentucky Republican must now juggle the difficult task of keeping those commitments.

Work between the House and Senate on a compromise tax bill is nearing completion — with some GOP aides speculating that a final package could be ready by early next week. Passing the first major overhaul of the tax code in decades would be a high point for the careers of McConnell and Speaker Paul D. Ryan.

But should Republicans succeed in getting the legislation to President Donald Trump’s desk before the upcoming holiday break, the victory lap could immediately be overshadowed by the need to cut a deal to keep the government funded beyond Dec. 22, the new deadline after last week’s passage of a short-term extension to avert a shutdown.

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The stakes are high for Republicans, who control the White House and both chambers of Congress for the first time since 2006. McConnell is used to negotiating in tight situations, something he became familiar with in talks with a Democratic White House over the prior eight years.

Internal forces

But this time will be different, as it will be members of McConnell’s own party applying most of the pressure.

Maine Sen. Susan Collins is touting the commitment she received from McConnell to advance two bills by the end of the year intended to help stabilize the insurance markets created by the health care law.

The prevailing thought among Republican and Democratic aides is that both measures would need to be added to a pending bill to fund the government in fiscal 2018 in order to pass.

But that is easier said than done.

House GOP members are already questioning the promise McConnell made — something he can do little to push back on from his perch atop the Senate. And Ryan is not making his job any easier, as the Wisconsin Republican makes promises to his own conference that run counter to those from the Senate majority leader.

Collins said she remains optimistic, but that optimism is not shared among some GOP senators, Republican and Democratic aides, and health care lobbyists who remain doubtful McConnell can follow through on his pledge.

“I have had a lot of conversations, not only with my colleagues in the Senate, but with my colleagues on the House side and with the White House. I’ve talked to the president three times about this issue, and once again, I have no reason to believe that that commitment will not be kept,” Collins said Sunday on CBS’s “Face the Nation.”

Whether she would vote for a final tax bill — which could be considered by the Senate prior to whatever spending bill Congress opts to pursue — without that commitment met remains to be seen.

More complications

And while McConnell succeeded in bringing his party on board with the Senate’s version of the tax bill (only Sen. Bob Corker of Tennessee voted against it), the outcome of this week’s tax conference  could create new headaches.

For instance, Sen. Ron Johnson, who has emerged this year as a thorn in the side of leadership, seems ready to pursue the leverage he has on McConnell for his vote.

The Wisconsin Republican succeeded in pushing for changes to the treatment of pass-through entities in the tax bill. Leadership had to raise a deduction for those businesses from an initially proposed 17.4 percent to 23 percent, a change that required billions of additional dollars in offsets.

Johnson also received a commitment from McConnell to have a “seat at the table” on negotiations with the House on the pass-through provisions. What that means is still unknown, and Johnson was not included as one of the eight GOP senators selected for the conference committee.

How that conference opts to bridge the gap between the two distinct proposals to address pass-through businesses could draw a rebuke from Johnson, although the senator has largely ended up toeing the party line despite protests on health care and taxes this year. 

Johnson said he has spoken with GOP members of the tax conference about how they are considering treating pass-through businesses in a still unreleased compromise bill.

“I’m more than willing to be flexible. It sounds like they’ve got some interesting ideas” he said Monday.

Johnson declined to say whether the House and Senate conferees were discussing combining each chamber’s respective proposal into one.

Opposition antics

Then there are the Democrats, who relish making McConnell’s path more perilous.

The minority party is gunning for major policy riders in the upcoming spending bill, including legislation to address the pending expiration of the Deferred Action for Childhood Arrivals program, or DACA.

While GOP congressional leaders and Trump continue to maintain a hard-line position against including any permanent solution to the program that oversees undocumented immigrants brought to the country as children in a spending bill solution, support from Democrats will be necessary in the Senate, where Republicans hold only 52 seats. (Funding legislation requires 60 votes to pass.)

“We don’t want to see the government shut down. We want to move forward in a bipartisan fashion to solve our problems. We believe that DACA is central,” Senate Minority Whip Richard J. Durbin of Illinois said Sunday on “Face the Nation.”