By Nathan Layne ATLANTA (Reuters) -Democratic Senator Raphael Warnock and Republican football legend Herschel Walker faced off on Tuesday in a final election that will determine whether Democrats can expand their razor-thin majority in the U.S. Senate and solidify Georgia as a battleground state in the next presidential election. The race will also be a last test of Donald Trump’s clout with voters as he seeks the Republican nomination to challenge President Joe Biden in 2024. The former president had a mixed record in his most competitive endorsements for Congress in the November midterm elec…