If the House does impeach President Trump, it would be up to the Republican-controlled Senate to decide whether he is removed from office. Just a handful of Republicans have raised concerns over the president's contacts with foreign leaders but there does not seem to be a unified defense of the president.

Privately, some Republicans say it just isn't worth it to take him on even if they disapprove of his actions, reports CBS News' Nancy Cordes. One reason why? The president hits back, and his approval rating within the Republican Party is strong. The latest Gallup Poll – which was taken as reports of the president's call to Ukraine unfolded – came in at 87%.

Maine Senator Susan Collins is one of the few Republicans willing to call the president out, also telling the Bangor Daily News, "I thought the president made a big mistake by asking China to get involved in investigating a political opponent."

Nebraska Republican Ben Sasse responded "Americans don't look to Chinese commies for truth" and Utah's Mitt Romney called the president's plea "wrong and appalling." Mr. Trump responded by calling Romney a "pompous 'ass'" and a bunch of other things.

Still, most Republicans have downplayed Mr. Trump's actions or stayed silent, but defending him has gotten more difficult.

"I doubt if the China comment was serious, to tell you the truth," Republican Sen. Roy Blunt said on "Face the Nation" this Sunday. Asked if he doesn't take the president at his word, Blunt said, "The president was—no, the president loves to go out on the—on the White House driveway. I haven't talked to him about this. I don't know what the president was thinking. But I know he loves to bait the press."

During a heated interview on "Meet the Press" Sunday, Republican Sen. Ron Johnson also struggled to defend the president, saying that the reason he winced when he heard about military aid being tied to Ukrainian investigations was, "because I didn't want those connected … when I asked the president about that, he completely denied it. He adamantly denied it."

A congressional source tells CBS News that Gordon Sondland, the former U.S. ambassador to the EU who also pushed Ukraine to investigate the Bidens, will appear for a closed-door deposition Tuesday.

Sondland was one of several people whose text messages revealed just how much pressure the Trump administration put on Ukraine to investigate a company linked to former Vice President Joe Biden's son.