WASHINGTON (AFP) - US President Barack Obama suffered another setback Monday as a fifth Democratic senator, centrist heavyweight Evan Bayh, opted not to run for re-election in dismay at the bitter political climate. Obama, who reportedly tried to talk Bayh out of retiring, faces a looming Republican resurgence and risks seeing strong majorities in Congress crumble in November mid-term elections, taking with them his ambitious reform agenda. With his tearful wife and two sons at his side, Bayh, 54, expressed disenchantment with excessive partisanship as he announced his decision at a press conference in his home state of Indiana. For some time, I have had a growing conviction that Congress is not operating as it should. There is too much partisanship and not enough progress-too much narrow ideology and not enough practical problem-solving, he said. Even at a time of enormous challenge, the peoples business is not being done. Democrats expressed shock at the development, seeing it both as the loss of a key consensus builder in the Senate and of a candidate strongly favored to win re-election in Republican-leaning Indiana. Bayh called Obama on Monday morning and The New York Times reported that both the president and his chief of staff, Rahm Emanuel, tried to convince him to run again, but to no avail. In a statement, Obama praised Bayh for reaching across the aisle on issues ranging from job creation and economic growth to fiscal responsibility and national security. I look forward to continuing to work with him on these critical challenges throughout the rest of the year, he said. Republican Dan Coats, a former senator who later served as US ambassador to Germany, recently announced he would challenge Bayh, who has never lost an election in Indiana and once considered running for the presidency. The son of Indiana senator Birch Bayh, he was best known as a moderate who co-sponsored a 2002 Senate resolution authorizing the Iraq war. He is a centrist, and it seems that the center is not holding, said Diane Ravitch of the Brookings Institution in a posting on Politico.Com. If senators such as Bayh leave or lose, the rancor in Washington will get louder and meaner. His decision not to run for a third term was the latest sign of trouble for Obama and the Democrats as they head into mid-term elections amid rising public anger over high unemployment and economic uncertainty. Explaining his disenchantment, Bayh pointed to last weeks collapse of legislation aimed at creating jobs and a Senate vote against a bipartisan commission to deal with the exploding deficit and debt. After all these years, my passion for service to my fellow citizens is undiminished, but my desire to do so in Congress has waned, Bayh said. There are better ways to serve my fellow citizens. I love working for the people of Indiana. I love helping our citizens make the most of their lives, but I do not love Congress. Bayh could easily have won re-election, making his decision all the more frustrating for Democrats struggling to hang on to the large majorities they won in 2008. A poll last week showed Bayh, who was reported to have 13 million dollars in his campaign chest, with a 20-point lead over Coats. The loss last month of the Senate seat in Massachusetts held for decades by the late Edward Kennedy stripped Democrats of the 60-seat super-majority they need to override Republican delaying tactics in the 100-seat chamber. Bayh is the fifth Democratic senator to opt not to run for re-election in 2010, a list that includes other party heavyweights Christopher Dodd of Connecticut and Byron Dorgan of North Dakota. It was unclear who would succeed Bayh as the Democratic candidate from Indiana. Possible contenders include Representatives Baron Hill and Brad Ellsworth. In a political climate clearly unfavorable to incumbents, there was a second surprise as a conservative radio talkshow host mounted an unlikely challenge to Republican former presidential candidate John McCain. John David J.D. Hayworth attacked McCain, 73, for pandering to liberals as he announced he would take on the popular Arizona senator in the state primary, setting up an ugly battle for the Republican party.