WASHINGTON - Opposition Republican party candidates won most of the competitive races in the 2014 midterm elections, taking control of the US Senate and a number of state governorships.

President Barack Obama will thus face a unified Republican-controlled Congress for his final two years in office.

Senate Minority Leader Mitch McConnell, a Republican from Kentucky, will become majority leader in January after he glided to re-election Tuesday against Democratic Secretary of State Alison Lundergan Grimes. In a quick move, Obama asked congressional leaders to meet with him at the White House on Friday.

“We do have an obligation to work together on issues where we agree,” McConnell said Tuesday evening in his victory speech. “Just because we have a two-party system doesn’t mean we have to be in perpetual conflict.”

Senate Majority Leader Harry Reid, the Nevada Democrat, released a statement conceding that his party had lost control of the chamber and congratulating his Republican counterpart, just-reelected Senator McConnell. “The message from voters is clear: they want us to work together,” Reid said. “I look forward to working with Sen. McConnell to get things done for the middle class.”

The Senate alone didn’t tell the full story of the Republican sweep: Across the map, Republican candidates startled Washington – including leaders in their own party – by ousting entrenched Democratic lawmakers and beating back energetic challengers on difficult turf.

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. Places where Democrats were favored, 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 favored, including Obama’s home state of Illinois.

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 favor of fresh legs. Obama, who was first elected in 2008 and again in 2012, watched election returns from the White House, and saw little to warm his spirits.

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Before the election results, the White House had signaled 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.  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.

 Reuters adds: Senator John McCain’s voice just got a whole lot louder.

One of President Barack Obama’s noisiest detractors, McCain is expected to take the helm of the powerful Armed Services Committee in the new Republican-controlled US Senate when the US Congress convenes in January.

The Arizona senator, a critic of the $399 billion Lockheed Martin Corp F-35 fighter jet program, is likely to push for tougher congressional scrutiny of costly US weapons programs, defense analysts say.

He has in the past launched investigations into waste in the US defense industry and shaped legislation to end cost overruns on major arms programs as a senior member of the Senate committee. McCain, a former Navy pilot and Vietnam War prisoner who lost to Obama in the 2008 election, has also criticized the administration on everything from fighting Islamic State militants to arming moderate Syrian rebels, while seeking a tougher US response to Russian aggression in Ukraine. As committee chairman he could summon Pentagon officials to public hearings to explain their strategy on Syria.

He has challenged the US Air Force to end a monopoly rocket launch program with Lockheed and Boeing Co, the Pentagon’s top two suppliers, and is pushing for development of a new US rocket engine to end reliance on Russian-built engines that power one of the firm’s rockets.

In his new position, McCain would oversee policy legislation that underpins the Pentagon’s budget, although the House and Senate appropriations committees oversee the Pentagon’s actual finances.

He would play a major role in writing the annual defense authorization bill. It sets policies on everything from defense spending and new weapons to military base closures and the elimination of specific weapons programs. The committee does not control how much money the Pentagon gets, but because it sets policies, it can control how the money is spent.

“I wouldn’t forecast any huge shifts right away,” said one defense industry executive, speaking on condition of anonymity, noting that McCain had worked closely for years on acquisition reform and weapons oversight with Carl Levin, the Michigan Democrat who now heads the committee.

The executive said companies and defense officials were bracing for more requests for information, briefings and hearings from a McCain-led panel.

US weapons makers are wary of what they see as McCain’s propensity to exaggerate problems when they occur, and worry that he does not understand their need as publicly traded companies to generate profits for shareholders.

But, McCain also offers them a ray of hope. He wants to ease automatic across-the-board cuts in military spending that are squeezing defense industry revenues.

McCain’s office did not respond to requests for comment.

If McCain becomes chairman, he is expected to focus oversight on weapons programs that failed to meet their targets for cost and delivery schedules, said Brett Lambert, a former senior Pentagon official and industry consultant.