WASHINGTON — Most presidents kick off their re-election campaigns with a speech on the campaign trail somewhere, or from the Oval Office. President Obama did it in a novel, telling and shrewdly chosen place: in the middle of an address to Congress.If people were wondering what template Barack Obama would choose for his re-election effort — some had suggested FDR in 1936 or Ronald Reagan in 1984 — we now have an answer:Harry Truman in 1948, the “Give ‘Em Hell Harry” who challenged Congress to tackle with the post-war nation’s problems and castigated the Republican Congress for its obstinate failure to do so.Addresses to joint sessions of Congress are supposed to be august, stately and somber affairs, but the president turned it into a raucous and lively mixture of a campaign stump speech and a college-style debate on the floor of the British House of Commons.His tactical strategy is clear. The only political institution less popular than he is at this time is the Congress. An astounding, almost pre-revolutionary 82 percent of the American people think that the Congress is doing a bad job of dealing with the nation’s problems.