Republicans suddenly face big pressure to deliver on promises to members that they’ll vote soon on some of the day’s biggest, most volatile issues — including how to deal with immigrant children, extend a children’s health program and permit government surveillance.

As Republican congressional leaders last month raced the calendar to deliver a tax bill and keep the federal government operating, they made a series of pledges to wavering members, sometimes in exchange for their crucial votes.

Sen. Jeff Flake, R-Ariz., was promised the Senate would take up a fix to the dilemma of immigrant children facing deportation. House members skeptical of the federal government’s controversial surveillance power were assured they’d get a full airing. Sen. Susan Collins, R-Maine, was told the Senate would vote on health care measures that would ease the end of the Obamacare mandate.

Starting Wednesday, when the Senate returns to begin its 2018 session, those IOUs are in play. The House is back Jan. 8.

The promises that threaten to further complicate congressional efforts to keep the government running:

Surveillance: House Speaker Paul Ryan, R-Wis., last month nearly faced a mutiny from libertarian-minded conservatives. Many expected a debate on changes to a controversial provision of the Foreign Intelligence Surveillance Act. But Ryan forced them to passively green light a re-authorization in a late December spending deal that expires Jan. 19.

With hours left before last month’s potential government shutdown, the conservative House Freedom Caucus held an emergency meeting to decide whether it would collectively oppose the spending bill. Section 702 of FISA currently allows the National Security Agency and FBI to monitor electronic messages of non-Americans without a warrant, but does not ensure Americans won’t also have their communications intercepted.

Ryan promised a full debate on the provision in the new year. He now has to deliver on that pledge or risk alienating nearly three dozen members already suspicious of his tactics.

The Senate may not be so accommodating. Senate Majority Leader Mitch McConnell, R-Ky., told McClatchy late last month he had made no such guarantee to his members about a FISA vote.

“I don’t know how it will be packaged,” McConnell said. “I don’t know what we’ll do on our side.”

Immigrant children: Flake says the White House and Republican leadership promised him in exchange for his vote in favor of the GOP tax reform bill that they would work on “fair and permanent protections” for undocumented young adults who came to this country as young children.

Many of the so-called Dreamers were protected from deportation under an Obama administration executive order known as Deferred Action for Childhood Arrivals, or DACA. President Donald Trump revoked the order in September and some undocumented immigrants say they are already losing protection, though Trump has promised to give Congress until March to fix the situation.

Flake said he has a promise from McConnell that a vote will take place before Jan. 19.

Trump has made the case more challenging, insisting that he wants money to build a wall at the border with Mexico.

Democrats have suggested they could support more border security funding in exchange for a DACA fix, but have resisted calls for wall money.

“Anybody that thinks you are getting an immigration fix without enhanced border security is just whistling past a political graveyard,” Rep. Tom Cole, R-Okla. told CNN on Tuesday.

Children’s health insurance: Nearly every lawmaker has promised to re-authorize the popular Children’s Health Insurance Program.

Democrats blame Republicans for offering to pay for it by gutting an office created through the Affordable Care Act. Republicans blame Democrats for not being willing to compromise to ensure roughly 9 million lower-income children are eligible.

Leaders last year did little to find consensus on anything more than a short-term fix, which wasn’t satisfactory to a lot of rank-and-file members.

To make it clear they’re serious about coming up with a long-term solution, though, those leaders opted to extend current CHIP funding through March. Still, Congress must make the time to negotiate, and it may have to act sooner to guarantee some states don’t run out of money early.

Defense: Some defense hawks in the House reluctantly voted last month for the end-of-the-year spending bill with assurances that the Pentagon will get a major budget increase.

The defense hawks had sought a budget giving given the Pentagon a major increase and enough money to last through the fiscal year, which ends Sept. 30.

Republicans want a major defense buildup and to increase defense spending by $54 billion. Non-defense programs would be increased by $37 billion this year.

Democrats want equal increases in the two sides of the budget and their votes are critical in the Senate, which will have 51 Republicans, 47 Democrats and two independents who caucus with Democrats.

Health care: Collins, a key vote for Republicans on the tax bill, reached a deal with Senate leadership to vote for overhaul in exchange for two health care fixes she says would address a provision in the tax bill that repeals the Obamacare individual mandate.

Collins had wanted the votes before the tax bill was finalized but said she still has a commitment from McConnell that the legislation will be considered.

“There is every reason to believe that these important provisions can and will be delivered as part of a bipartisan agreement,” Collins said late last month. The two provisions aimed at stabilizing the insurance markets by providing cost-sharing payments and providing for high-risk pools include one co-sponsored by Sens. Patty Murray, D-Wash. and Lamar Alexander, R-Tenn., and another backed by Collins and Sen. Bill Nelson, D-Fla.

House conservatives consider the measures a bailout for the insurance industry, but Collins said she’s talked to Ryan who told her that the House “remains committed to passing legislation to provide for high-risk pools and other reinsurance mechanisms.”