PATRICIA ZENGERLE and RICHARD COWAN IN a dramatic day in the U.S. Congress, Vice President Mike Pence rejected Donald Trump's demand that he try to overturn the results of the presidential election and the Senate's top Republican denounced a bid by the president's allies to challenge Trump's loss to Democrat Joe Biden. Pence, a loyal lieutenant during the four years of Trump's tumultuous presidency, presided over the opening of a joint session of Congress to formally certify Biden's November 3 victory over Trump. A band of Republican lawmakers quickly challenged the results, first from the election battleground state of Arizona…