President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE on Thursday night dismissed former President Obama's reemergence on the campaign trail ahead of the November midterm elections, arguing it could fire up his own base.

“By the way, he’s campaigning again. That’s good news. When I was running, I swear, I thought he campaigned harder than Hillary Clinton Hillary Diane Rodham ClintonDemocratic groups using Bloomberg money to launch M in Spanish language ads in Florida The Hill's Campaign Report: Presidential polls tighten weeks out from Election Day More than 50 Latino faith leaders endorse Biden MORE. And we won big,” Trump said at a rally in Las Vegas on Thursday evening.

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Obama burst back onto the scene earlier this month in a speech in Illinois that included blistering rebukes of Trump’s performance while in office on everything from his tax plan to his response to the deadly white nationalist rally in Charlottesville, Va., last year.

The former president also travelled to California to rally for several House candidates, including some running in Republican-held districts, and Ohio to campaign with Democratic gubernatorial candidate Richard Cordray Richard Adams CordrayConsumer bureau revokes payday lending restrictions Supreme Court ruling could unleash new legal challenges to consumer bureau Supreme Court rules consumer bureau director can be fired at will MORE.

Obama will also travel to Philadelphia on Friday to rally with Democratic Sen. Bob Casey Robert (Bob) Patrick CaseySecond GOP senator to quarantine after exposure to coronavirus GAO report finds brokers offered false info on coverage for pre-existing conditions Catholic group launches .7M campaign against Biden targeting swing-state voters MORE and Gov. Tim Wolf (D).

Obama had previously avoided the campaign trail since leaving office, wary of nationalizing tight state races or rallying GOP voters in some areas.

Trump's comments came during a rally in Nevada on behalf of Sen. Dean Heller Dean Arthur HellerOn The Trail: Democrats plan to hammer Trump on Social Security, Medicare Lobbying World Democrats spend big to put Senate in play MORE (R-Nev.), one of the most vulnerable Republicans running for reelection in November.