Approval numbers in the US often correlate with the numbers of voters who would vote to put you into office if elections were held that day. The president’s party is also held responsible for the mistakes he makes so Obama’s low numbers means that vulnerable congressmen and senators will have a rough go in the 2016 November electons. If the president’s numbers were relatively high...say 55 or 60 per cent, then the legislators up for election wouldn’t mind “riding his coat tails” and would welcome an appearance by the president upon their behalf. Right now, Dem legislators who hail from conservative leaning states are asking are asking Obama to stay away from them until the elections are over.
Approval numbers are supposed to be derived from tallies of total numbers of voters from all parties with statistical weightings based on what is known about the numbers making up each of the major parties. Overall there are more registered Democrats in the US vs Republicans...but there are large numbers of unaffiliated voters or those who refuse to give a party preference when the pollsters contact them for their opinions. Time of day,day of week, land lines or cell phones, employed during the day verses non working welfare Oprah watchers, all these can affect “sampling” of data.
There is a tendency in the US amongst the media to over “weight” Democrats” in the sampling vs Republicans...thus a 38 per cent approval rating, giving Obama every weighted advantage in the polling, points to even more horrible numbers for the president , should absolute non weighted polling numbers ever be applied to him!