(CNN) -- 2012 has been a tumultuous year in American politics. With the presidential election capping off the year, Americans have witnessed a series of bitter domestic battles and turbulent events overseas. As the year closes out, it is worth thinking about some of the most important lessons that politicians and voters can learn from this year as they prepare for 2013. Here are six: The Republican brand name is in trouble: The GOP took a drubbing in 2012. To be sure, Mitt Romney ran a problematic campaign. His inability to connect with voters and a number of embarrassing gaffes hurt the chances for Republicans to succeed.
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Julian Zelizer: 2012 was a year of bitter domestic battles, turbulence overseas
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He says the weakness of GOP, renewed strength of liberalism were apparent
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Zelizer says the year also highlighted the influence of new immigrants in America
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Zelizer: Year ended with a tragic reminder about need to act on gun control
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