Obama, the two-term president still highly popular among Democrats, laid out a biting indictment of the Trump administration at rallies on Saturday for Virginia gubernatorial candidate Abigail Spanberger and New Jersey candidate Mikie Sherrill.
"Let's face it, our country and our policy are in a pretty dark place right now," Obama told a roaring crowd of Spanberger supporters at Old Dominion University in Norfolk, Virginia.
"It's hard to know where to start," he said.
"Because every day this White House offers people a fresh batch of lawlessness and recklessness and mean-spiritedness and just plain craziness."
Obama blasted what he called Trump's "shambolic" tariff policy and deployment of National Guard troops to US cities and criticised Republicans in Congress for failing to check Trump "even when they know he's out of line".
He said he was surprised at how quickly business leaders, law firms and universities opted to "bend the knee" to appease Trump.
Later on Saturday at an event in Newark, New Jersey to support Sherrill, Obama struck many of the same themes as he continued his criticisms of the Trump White House.
"It's like every day is Halloween, except it's all tricks and no treats," Obama said.
The former president occasionally dipped into sarcasm in mentioning Trump decisions such as remodelling parts of the White House even as a federal shutdown continues.
"In fairness he has been focused on some critical issues, like paving over the Rose Garden so folks don't get mud on their shoes, and building a $US300 million ($A457 million) ballroom," Obama said.
Polls show Spanberger, 46, with a sizable lead over the Republican candidate, Lieutenant Governor Winsome Earle-Sears, 61. Spanberger, a former CIA officer, was a congresswoman for six years.
Most polls show Sherrill with a single-digit lead over Republican Jack Ciatterelli, 63, a former state assemblyman making his third consecutive run for the governor's seat.
