(CNN) -- The Republican 2016 presidential field is starting to come into focus with potential contenders making notable moves this week. Here's a breakdown of the latest headlines starting to shape the early race for the Republican nomination. Portman is out Pollsters can cross one name off their long list: Rob Portman. The Ohio Republican announced Tuesday he's running for re-election to his Senate seat. Portman was vetted, but ultimately not picked, to be Mitt Romney's running mate in 2012, and he would have been the first pro-same sex marriage Republican presidential candidate if he ran this cycle. He said as recently as two weeks ago that he was considering a presidential run, telling CNN's Erin McPike that he "probably (has) more experience than other people who are running or thinking about running."
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Rob Portman announced he won't run for president in 2016
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Jeb Bush, however, said he's still "thinking" and will make a decision soon
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A new CNN poll shows Mitt Romney is still the top favorite, wtih Ben Carson in second
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Rand Paul and Chris Christie are also making moves toward 2016
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