Washington (#CNN) A wide array of House and Senate Republicans are not yet ready to endorse President Donald Trump’s bid for a second term, a reflection of the deep uncertainty on Capitol Hill over his political standing amid growing problems at home and abroad.In interviews with a cross-section of more than two dozen GOP lawmakers, ranging from rank-and-file members, conservatives and party leaders, many refused to say they’d back Trump’s re-election bid — a surprise declaration given that members of Congress are typically quick to endorse sitting presidents of their own party without hesitation. Hardly any would offer a categorical endorsement of the President.“I don’t know what the world is going to look like,” said Senate Majority Whip John Cornyn, a Texas Republican, when asked if he’d endorse Trump for re-election. “But let’s say it’s not something I’ve given any thought to.”Asked several days later if he had given thought to it, Cornyn demurred.“I haven’t even thought about that election,” said Cornyn, No. 2 in the Senate GOP conference. “I’m worried about the midterm election.”He’s not alone. Many lawmakers sought to avoid the topic altogether.“Look, I’m focused on opioids,” said Sen. Lamar Alexander, the veteran Republican from Tennessee, referring to efforts in Congress to deal with the drug epidemic. “And I was just reelected myself three years ago. So, I’m focused on that.”And others said they were still uncertain the President would ultimately stand for re-election — even though the White House and Trump himself have repeatedly said he would do so, as he’s hired a campaign manager, has been raising money and holding campaign rallies in anticipation of 2020. Unlike past presidents who have waited to announce their reelection bids, Trump made clear immediately after taking office that he’s running again.Still, many Republicans aren’t certain he’ll do it.