Defeats at home and Mr Obama's policies abroad

It has been hard enough for Barack Obama to change Washington and US foreign policy in his first two years as president. Starting today, it will only become more difficult.

Mr Obama's party, the Democrats, have controlled both the US Senate and House of Representatives since his inauguration. But as a result of today's mid-term elections, that is almost certain to change. Every seat in the House and one-third of seats in the Senate are up for grabs as Americans go to the polls. Mr Obama's party faces a rout.

As he prepares for his own re-election campaign in 2012, it will be difficult if not impossible for Mr Obama to pass much of his domestic agenda. To bolster his battered image at home, he may be tempted to look for victories abroad. Republican gains in Congress will also make this more difficult.

The Israeli-Palestinian peace process will present the first chance to see what Mr Obama has learned from his party's defeat. His hand may be weaker in Washington, but Mr Obama remains the only one who has the tools to change Mr Netanyahu's behaviour. He must use them to get the Israelis and the Palestinian Authority back to the negotiating table. And with the damage already done to his own party, Mr Obama may have less to lose from getting tough on Israel.

Republicans will also be tougher on Mr Obama for his conduct of the war in Afghanistan. Historically, Republicans have found success in criticising the Democrats as weak on defence. They will have another opportunity to do so next summer, when Mr Obama has said that US troops will begin withdrawing from Afghanistan.

Iran may prove trickier still. Republicans have urged a tougher line against Tehran and as they gain in influence, calls for military action will only grow louder. Mr Obama's instincts may favour patience and diplomacy but his political survival may dictate that he take far stronger action. And while a nuclear Iran will certainly make the region less secure, so would the fallout of another bungled US intervention.

Mr Obama must also contend with imbalances in the global economy, and in particular, with how to engage China in helping to resolve them. China's importance to the global economy is only growing. And yet, both Republicans and Democrats will be eager to use China as a scapegoat for many of America's economic woes. Calls for protectionist policies against China, or even a trade war, will become more common if unemployment in the US remains high. Members of Congress will see a short term political benefit in advocating tougher measures against China but enacting them could put the global economy's recovery at risk.

If popular anger in the US spawns protectionist policies, it is not only those in the US and China whose prospects will be dimmed. Indeed, cooling tempers at home may be the greatest challenge for Mr Obama in the next two years.