WASHINGTON — For once, President Trump is showing no hard feelings. A week after being booed at Nationals Park, the president will host the Washington Nationals at the White House on Monday to celebrate an improbable come-from-behind World Series victory that has united an otherwise polarized nation’s capital.

But not every member of the championship team plans to make peace with the president on the South Lawn. Sean Doolittle, the star reliever who has been vocal on social issues, including Syrian refugees, says he will not attend a ceremony hosted by a president who empowers white supremacists and mocks disabled people.

The White House invitation, and the difficult choices it entailed for the team, came as Washington marked its first World Series championship team since 1924 with a parade down Constitution Avenue and a rally near the Capitol on Saturday. Republicans, Democrats and everyone in between planned to head downtown to cheer on the sluggers and pitchers who somehow came from 12 games below .500 in the spring to beating the mighty Houston Astros in the Fall Classic.

Their story of persistence, grit and character has been held up as a tonic for a city marked by the coexistence of a largely liberal populace and a Congress that has grown even more deeply divided under Mr. Trump. The day after the Nationals took Game 7 in Houston, becoming the only team to ever win four road games in the World Series, the House voted to authorize an impeachment inquiry against the president, setting the stage for a momentous constitutional clash.