For once, President-elect Joe Biden’s Democratic Party seems all set to have a fair measure of control in both Houses of Congress, after his party’s stunning success in Georgia, but key reforms on healthcare and climate change cannot be assured a smooth ride.

Raphael Warnock’s win of one of the state’s US Senate seats and Jon Ossoff’s lead in the race for the other in Tuesday’s runoff elections looked likely to give Democrats control of both chambers in Congress and the White House, although a winner had yet to be projected in Ossoff’s contest.

And even if Democrats take the Georgia seats, they would achieve a majority only with a tie-break vote from Vice President-elect Kamala Harris, leaving them far short of the 60 votes needed for most major spending legislation outside of normal budget reconciliation rules.

With the Senate divided down the middle, compromise with Republicans will be necessary for Biden to get anything substantial done, and his most ambitious pieces of legislation may have to wait even though the party’s progressives will push him and Democratic leaders to move ahead.  In the short term, Biden’s executive and judicial nominees will have an easier time getting confirmed, which requires only a majority vote. His administration also may be able to dodge harassing probes with Democrats taking over from Republicans the chairmanships of Senate committees.

More important, Democrats and the new majority leader, Chuck Schumer, will have the power to control the Senate calendar and which bills are brought to the floor for a vote.

Schumer and Pelosi will preside over razor-thin Democratic majorities, however, leaving little margin for error and potentially emboldening Republicans to obstruct their agenda as much as possible. Even so, Schumer on Wednesday promised to deliver “bold change.” “Senate Democrats know America is hurting,” he said. “Help is on the way.”

It could be a tough two years for Biden.

His initial moves will be measured. He is expected to request just under $1 trillion in additional COVID-19 relief funding, a package that will include economic stimulus, support for state and local governments, and money to reopen schools and distribute vaccines.

There is likely to be little appetite among Republicans for supporting a second round of $1 trillion-plus spending after Biden takes office on January 20 – a task considered to be all the more difficult were the Republicans to retain control of the Senate.

Schumer on Wednesday said sending most Americans $2,000 cheques – an effort that died in the Senate when Republican Majority Leader Mitch McConnell refused to allow a floor vote – would be a top priority in the new Congress. During the 2020 presidential campaign, Biden spoke in sweeping terms about being a Democrat in the mould of Franklin Roosevelt, pledging action on issues such as immigration, climate change, healthcare and economic inequality.

While the tight margins in the House and Senate will make that difficult, if not impossible, some Democrats say Biden should not back down from trying to advance an ambitious agenda.

Schumer can force moderate Democrats and Republicans to take votes on big-ticket packages such as Biden’s $2 trillion clean-energy plan.

Biden plans on issuing a flurry of executive orders upon taking office on matters such as immigration, where he would reinstate the Deferred Action for Childhood Arrivals programme for so-called “Dreamers” and curb deportations. On climate, he would have the United States rejoin the Paris climate accord and reverse many Trump administration environmental policies. Yet Biden also must think about the longer term. As vice president under Barack Obama, he watched as Obama pursued an aggressive early agenda involving healthcare and climate change. In the 2010 midterm elections, Republicans seized upon those polarising efforts to regain control of the House.

This time around, Republicans may be uninterested in cutting deals with Biden, preferring to wait Biden out in the hope they can flip control of both chambers in 2022.