Answer: 35%
Further detail: You didn't show us the graph, so I'll attach a graph from the Pew Research Center that shows party identification numbers from 1992 to 2012. In 2012, the data points were as follows:
- Identifying as Democrat: 35%
- Identifying as Republican: 28%
- Identifying as independent: 33%
In the graph image I've attached, the second graph shows the percentages favoring Democrat or Republican when including which direction the independent voters said they leaned. In 2012, the percentage of voters identifying as Democrat plus those independents leaning Democrat was 48%, and the percentage identifying as Republican or leaning Republican was 43%.
You'll notice that the gap between those favoring Democrat vs. those favoring Republican narrowed between 2008 and 2012. That meant President Obama's reelection victory in 2012 was a closer race than it had been when he was first elected in 2008. He won the Electoral College vote 365 to 173 in 2008, and his Electoral College margin in 2012 was 332 to 206.