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DAYTON, Ohio (Reuters) - President Barack Obama, America's basketball fan-in-chief, treated British Prime Minister David Cameron to courtside seats for "March Madness" on Tuesday, taking him to an NCAA tournament game in the presidential election swing state of Ohio.

The quick trip to Dayton to show off one of the country's most popular sporting events was intended to help underscore what has long been touted as a "special relationship" between transatlantic allies, the White House said.

Obama, an avid basketball fan, whisked Cameron out of Washington to attend the National Collegiate Athletic Association game between Western Kentucky and Mississippi Valley State at the University of Dayton sports arena.

Obama chatted with fans and leaned toward Cameron at times, explaining aspects of the game. In a bit of Americana midway through the first half, the two munched hot dogs and Cameron sipped a Coke. Western Kentucky won the game 59-58.

In a halftime interview with truTV, Obama noted both teams were shooting poorly. "It may be nerves," he said. "These are not teams that normally end up coming to the tournament."

Cameron said it was his first basketball game and the pace was "fast and furious." He said Obama helped him follow the action, while Obama said Cameron was going to return the favor by teaching him cricket.

"Because I don't understand what's going on with that cricket thing," Obama said.

Obama's law school alma mater, Harvard, made the NCAA tournament from the Ivy League. But he predicted Ohio State would be one of the tournament "Final Four" semifinalists.

Obama and Cameron will hold formal talks at the White House on Wednesday and the British prime minister will be honored at a state dinner on Wednesday evening.

The Ohio visit also carried a touch of domestic politics. Ohio is a battleground state in the November 6 election, crucial to Obama's hopes of securing a second term in the White House.

The Democratic president won Ohio in 2008 but polls show he faces a tough fight keeping it in his column if matched up against Republican front-runner Mitt Romney.

At the same time, Obama had a chance to strengthen his personal bond with Cameron. When Obama visited Britain last May, the two leaders took on a pair of teen-age boys in table tennis.

Obama regularly plays pickup basketball and attends his daughters' games. He has also made it a tradition, like millions of Americans, to predict winners of the match-ups between college teams in the "March Madness" championship tournament. The White House will soon publicize his bracket picks.

But Cameron's visit will be about more than just fun and games. The leaders will discuss the war in Afghanistan, the Iran nuclear standoff, violence in Syria and the global economy.

(Reporting By Matt Spetalnick; editing by Todd Eastham)