The president frustrated labor allies when he refused to campaign against Walker during the 2012 recall race.

“I’ve got a lot of responsibilities,” Obama said as an excuse for his failure to appear on the stump for Milwaukee mayor Tom Barrett, who was challenging Walker.

Obama’s willingness to campaign on behalf of Democratic gubernatorial candidate Mary Burke could be a sign that they believe Walker is more vulnerable this time around than during the recall race. Walker won the recall by almost seven points, but a poll from Marquette University has him trailing by two points among likely voters, but winning by three among registered voters. That’s an odd result, because “Republican candidates typically poll better among likely voters, particularly in midterm elections when Democratic-leaning constituencies are less likely to turn out,” as FiveThirtyEight’s Harry Enten notes.

Or maybe the president is more willing to risk backing a losing candidate because he’s not on the ballot himself. In any case, he should take some time to mend fences with the unions at Laborfest.