Former President Barack Obama is poised to plunge into the fray of the midterm campaign, returning to electoral politics with a frontal attack on Republican power in two states that are prime Democratic targets this fall: California and Ohio.

Having largely avoided campaign activities since leaving office, Obama's first public event of the midterm election will take place in Orange County, a traditionally conservative-leaning part of California where Republicans are at risk of losing several House seats. And Obama is expected to be joined by Democratic candidates from all seven of California's Republican-held districts that Hillary Clinton carried in 2016.

Obama intends to campaign next Thursday in Cleveland for Richard Cordray, a former bank regulator in his administration who is the Democratic nominee for Ohio governor. Republicans have held total control of the state government since the 2010 election, and Obama helped encourage Cordray, also a former state attorney general, to seek the governorship.

The former president's return to public politicking comes at a momentous point in the 2018 election season, furnishing Democrats again with one of their most formidable and popular campaigners in the closing months. While Obama has addressed several fundraising events and issued a list of endorsements, he has otherwise confined his public appearances this year to loftier venues than the campaign trail.

Katie Hill, a spokeswoman for Obama, said he would campaign to turn out voters in elections for the House and Senate and also "in local, down-ballot races to build the Democratic Party's bench."

Hill said Obama would argue to voters "that this moment in our country is too perilous for Democratic voters to sit out."

Obama's upcoming campaign swing comes days after his oration for John McCain, the Arizona Republican, whose funeral last weekend became an occasion for scarcely veiled criticism of President Donald Trump from elder statesmen of both parties. Obama is also delivering a speech Friday at the University of Illinois at Urbana-Champaign.