Shifting explanations for withholding aid draw GOP alarm

(Evan Vucci | AP) President Donald Trump speaks during an event where he congratulated astronauts Jessica Meir and Christina Koch as they conduct the first all-female spacewalk, from the Roosevelt Room of the White House, Friday, Oct. 18, 2019, in Washington.Washington •The shifting White House explanation for President Donald Trump’s decision to withhold military aid from Ukraine drew alarm Friday from Republicans as the impeachment inquiry tested their alliance.

Trump, in remarks at the White House, stood by his acting chief of staff, Mick Mulvaney, whose earlier comments undermined the administration's defense in the impeachment probe. Speaking Thursday at a news conference, Mulvaney…