President Obama kicks off 2012 even-up on job approval in the new Washington Post-ABC News poll: 48 percent of Americans approve of the job he’s doing; 48 percent disapprove.

Four other post-war presidents started election years with sub-50 percent approval. Only one of them — Richard Nixon won re-election.

The data in this chart should set off a few warning signals for Obama. His approval rating among independents — at 43 percent — is on the low side. Only Lyndon Johnson had a numerically lower rating among independents at the outset of 1968, before opting out of a re-election bid.

The most prominent difference for Obama is the spike in partisanship. The gaping 70-point difference in approval between Democrats and Republicans is unrivaled compared with other presidents at this point. Only 13 percent of Republicans approve of Obama’s performance. No other president has had such low approval from the opposing party. His approval had been as low as 8 percent among Republicans in November.

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