HUNTINGTON, W.Va. — Bragging about keeping his promises on immigration, the economy, the environment and crime, President Trump celebrated on Thursday with a raucous West Virginia crowd as the state’s Democratic governor announced that he will switch to the Republican Party.

With Gov. Jim Justice by his side, Mr. Trump hailed stock market records and the growth of coal income in West Virginia. And he delivered a lengthy critique of the federal investigations of his campaign’s ties to Russia, calling the matter “a fake story that is demeaning to all of us.” His comments came just hours after reports that a grand jury had been impaneled in the Russia investigation and that subpoenas had been issued.

“Most people know there were no Russians in our campaign; there never were,” Mr. Trump told the crowd in a midsize rural town that drew thousands of supporters from across Appalachia, a region that gave Mr. Trump some of the largest margins of his election. “We didn’t win because of Russia; we won because of you,” he said. “Are there any Russians here tonight? Any Russians?”

The president also demanded that Congress pass a repeal of the Affordable Care Act, urging the crowd to call their lawmakers so they will have “the guts” to take a vote. He vowed to reduce taxes, continue to crack down on immigrants, and rebuild the country’s infrastructure.