The Republican rout was wide and deep in what was bound to be seen as a sharp rebuke to Obama, who has lurched from crisis to crisis all year and whose unpopularity made him unwelcome to Democratic candidates in many contested states.The Republicans also strengthened their grip on the House of Representatives. When the new Congress takes power in January, they will be in charge of both chambers of Congress for the first time since elections in 2006.The Republican takeover in the Senate will force Obama to scale back his ambitions to either executive actions that do not require legislative approval, or items that might gain bipartisan support, such as trade agreements and tax reform.It will also test his ability to compromise with newly empowered political opponents who have been resisting his legislative agenda since he was first elected. And it could prompt some White House staff turnover as some exhausted members of his team consider departing in favour of fresh legs.Obama, first elected in 2008 and again in 2012, called Democratic and Republican leaders of Congress to the White House on Friday to take stock of the new political landscape.He watched election returns from the White House, and saw little to warm his spirits.Before the election results, the White House had signalled no major changes for Obama. Officials said Obama would seek common ground with Congress on areas like trade and infrastructure."The president is going to continue to look for partners on Capitol Hill, Democrats or Republicans, who are willing to work with him on policies that benefit middle-class families," White House spokesman Josh Earnest said on Tuesday.Obama, a one-term senator before he became president, has often been faulted for not developing closer relations with lawmakers.He will find one familiar face in a powerful new position.Republican Senator Mitch McConnell of Kentucky, who won a tough re-election battle against Democrat Alison Lundergan Grimes, will replace Democrat Harry Reid as Senate majority leader. Reid has been one of Obama's top political allies and helped him steer the president's signature healthcare law through the Senate in 2010.“Some things don’t change after tonight. I don’t expect the president to wake up tomorrow and view the world any differently than he did when he woke up this morning. He knows I won’t either. But we do have an obligation to work together on issues where we can agree," McConnell said in his victory speech in Louisville.Toss-ups Become Republican WinsIn Tuesday's comprehensive rout, Republicans won in places where Democrats were favoured, taking a Senate race in North Carolina, pulled out victories where the going was tough, like a Senate battle in Kansas, and swept a number of governors' races in states where Democrats were favoured, including Obama's home state of Illinois.Of eight to 10 Senate seats that were considered toss-ups, Republicans won nearly all of them. They needed six seats to win control of the 100-member Senate, and by late evening they had seven.The winning margin came when Iowa Republican Joni Ernst was declared the winner over Democrat Bruce Braley and Republican Thom Tillis defeated incumbent Democratic Senator Kay Hagan in North Carolina.The Iowa race was particularly indicative of Republican fortunes. Ernst came from behind and surged in recent weeks despite herculean efforts by powerful Democratic figures to save Braley, including a campaign visit by Obama's wife, Michelle.Republican Senate candidates also picked up Democratic seats in Montana, Colorado, West Virginia, South Dakota and Arkansas.'Responsibility ... To Lead'Once the euphoria of their victory ebbs, Republicans will be under pressure to show Americans they are capable of governing after drawing scorn a year ago for shutting down the government in a budget fight. That will be a factor in their ambitions to take back the White House in 2016.Republican Senator Ted Cruz, a conservative firebrand who may run in 2016, told CNN: "The American people, they’re frustrated with what’s happening in Washington, but now the responsibility falls on us to lead."While there was talk of conciliation, no major breakthrough in Washington's chilly climate is expected soon.Partisan battles could erupt over immigration reform, with Obama poised to issue executive actions by year's end to defer deportations of some undocumented immigrants, and over energy policy, as Republican press the president to approve the Keystone XL pipeline carrying oil from Canada.Jay Carney, Obama's former spokesman, said he expects Obama to make an "all-out push" on his priorities regardless of the makeup of Congress.Whatever the case, Obama will face pressure to make changes at the White House. A Reuters/Ipsos poll showed 75 percent of respondents believe the administration needs to "rethink" how it approaches major issues facing the United States. Sixty-four percent said Obama should replace some of his senior staff after the election.The Republican victory had been widely predicted ahead of Tuesday's voting to elect 36 senators, 36 state governors and all 435 members of the House of Representatives.Obama and other White House officials blamed the electoral map - noting that many key Senate races took place in conservative states that Obama lost in 2012.Election Day polling by Reuters/Ipsos found a dour mood among the electorate with less than one-third of voters believing the country is headed in the right direction.Roughly 40 percent of voters said they approved of the job Obama is doing as president, though they were split over whether they expected the economy to improve or worsen in the coming year.In a consolation for Democrats, Jeanne Shaheen won re-election over Republican Scott Brown in New Hampshire in what polls had forecast as a tight race.In Virginia, heavily favoured Democratic incumbent Senator Mark Warner found himself in a surprisingly close fight against Republican challenger Ed Gillespie, with much of the vote counted. By late evening, he claimed victory but Gillespie had not yet conceded.In the most closely watched governors' races, Florida's Republican Governor Rick Scott edged out Democrat Charlie Crist, and Republican Scott Walker survived a challenge from Democrat Mary Burke in Wisconsin.