A lawsuit by the Justice Department challenging a potential narrow loss by the GOP Senate incumbent in Alaska reflects a new tactic by the president to try to shape the election results.
The 44th president sharply criticized Mr. Trump, who hit back later in the day. Mr. Obama also assailed Vivek Ramaswamy, the Republican nominee for governor of Ohio.
With moves in Alaska and California, the department has stepped up interventions in the midterm elections as the president’s instrument of unmediated executive power.
President Trump during a campaign rally in support of Senator Dan S. Sullivan in Wasilla, Alaska, this month. Mr. Trump urged the Justice Dept. to intervene in the Senate race.
No obvious legal authority supports a pre-emptive effort to block the certification of Alaska’s Senate election if the Republican incumbent narrowly loses.
The charges intensified the administration’s efforts to go after the law enforcement and intelligence personnel who cast doubt on unsubstantiated claims that Joseph R. Biden Jr. engaged in corrupt dealings in Ukraine.
Senators have warned the White House they will withhold confirmation votes until the administration ensures the restoration of communications capabilities used by Ukraine’s military.
Representative Brian Fitzpatrick, Republican of Pennsylvania and a former F.B.I. agent who worked on Russian counterintelligence in Kyiv, said he doubted the communication problems were accidental.