Complex sentence: After the primary elections, the race had been rated "Likely GOP" by RealClearPolitics, but that would be out of date, due to the campaign developments in September and October 2012.
Split into simpler sentences: After the primary elections, the race had been rated "Likely GOP" by RealClearPolitics. However, those analyses would be out of date, due to the campaign developments in October 2012.