As for message discipline and coordination with the White House, Thune deemed that 'a work in progress.'
Lawmakers gathered as the White House announced a series of executive actions aimed at building a border wall and cracking down on illegal immigration, and as Trump declared there would be an investigation into voter fraud although there is no evidence of the millions of illegal ballots he claims cost him the popular vote.
The Trump administration is also readying a sweeping review of how America conducts the war on terror, including possible resumption of banned interrogation methods, according to a draft executive order obtained by The Associated Press.
GOP lawmakers were welcoming the moves on immigration. 'The wall was a very big part' of Trump's campaign promises, Rep. Doug Collins, R-Ga., told reporters.
But the actions on election fraud and torture drew a sometimes skeptical response as lawmakers arrived in Philadelphia.
'This is a debate we've had already, we believe it is settled law,' Thune said on the issue of torture, which Congress has banned.
Football star Peyton Manning also was scheduled to appear at the retreat.
By ASSOCIATED PRESS
PUBLISHED: 22:17, 25 January 2017 | UPDATED: 23:44, 25 January 2017