Democrats arrived in Charlotte on Monday to an ill-timed reminder of one of the issues plaguing President Barack Obama’s reelection bid: high gasoline prices. Prices at the pump reached a national average of $3.83 Monday, according to AAA, setting a record high for a Labor Day. The previous Labor Day record of $3.69 was set in 2008, at the height of the last presidential election fight. Gas prices have increased by 23 cents in the past month during the height of the summer driving season. But AAA predicts that Obama, who has faced sustained attacks from Republicans over gas prices,...