In interviews with Axios, Republican senators Mitt Romney and Lindsey Graham discussed the impeachment inquiry into President Donald Trump that has been launched by House Democrats.

Sen. Lindsey Graham of South Carolina indicated he could be open to impeaching the president, if evidence emerged that Trump had engaged in a "quid pro quo" arrangement with Ukraine in an effort to secure compromising information on Democrat rival Joe Biden.

Sen. Romney of Utah listed reasons for impeaching the president, including racist rhetoric, extramarital affairs, and abandonment of the US' Kurdish allies in Syria.

As things stand, Democrats still appear to be far short of the 20 Republican allies they would need to remove the president from office after an impeachment trial.

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For most of his presidency, amid controversy and provocation, Trump has been able to rely on a so-called "red wall" of support from congressional Republicans, on top of his extremely solid support among the GOP grass roots.

But recent comments from two senators, and reports of widespread opposition from within his own party to his plans to host the G7 summit at his own Florida gold club, show that weaknesses exist.

In an interview with Axios TV, Sen. Lindsey Graham of South Carolina, usually among the president's staunchest allies, expressed rare exasperation at the president's behavior. He said he could still back impeachment if evidence emerged that the president had broken the law.

Calling Trump a "handful" and "an equal opportunity abuser of people," he addressed the whistleblower's complaint behind the impeachment inquiry, a document alleging that the president sought to trade military aid for political favors from Ukraine in a "quid pro quo" arrangement.

"If you could show me that, you know, Trump actually was engaging in a quid pro quo outside the phone call, that would be very disturbing," he said.

Sen. Mitt Romney of Utah went a step further in his interview with the outlet, listing the grounds for removing the president from office. Sources close to the senator — a longstanding critic of Trump — told the outlet he would be among the first to vote to convict Trump.

"He has elements, I'm sure, of honor in his life. And there's things that I think are not honorable. And I mention that because of the payment to a porn star for sexual relations outside of marriage," said Romney.

The remark was a reference to accusations from the president's former personal attorney, Michael Cohen, that Trump authorized hush money payments to porn star Stormy Daniels.

Mitt Romney speaks to journalists on January 24, 2019. Romney said he would be 'studying' a vote to block the president declaring a national emergency. Melina Mara/The Washington Post via Getty Images

Support for impeaching the president from a moderate Republican like Romney may encourage like-minded colleagues to follow suit.

According to reports from the Washington Post and The New York Times, the prospect seems to have the president spooked.

The publications reported that he reversed his decision to host the G7 summit at his golf resort in Florida after learning that moderate Republicans saw the decision as indefensible.

Earlier, Republican lawmakers had told the Post they were "repulsed" by the decision to hold the summit at the resort.

Trump's support from within his own party was already shaken by his decision to suddenly withdraw US troops from Syria, opening the way for Turkey to attacks the longtime Kurdish allies of the US, and to risk harming the fight against ISIS.

The wavering support comes at the worst time for Trump — with the Democrat-controlled House highly likely to vote to impeach the president, setting the stage for a Senate trial where the president needs the support of the Republican-held chamber if he is to avoid becoming the first ever president removed by impeachment.

Amid signs of weakness, the president is reportedly keeping a close eye on support from within his party, calling Senate Majority Leader Mitch McConnell up to three times a day to attack lawmakers he sees as disloyal in a bid to shore up support.

The president seems to have believed up to this point that he could always count on Republican support, which may explain why, despite facing impeachment, he continues to stir controversy with decisions like the G7 venue.

IN this March 13, 2019, photo, reporters pose questions to Sen. Lindsey Graham, R-S.C., at the Capitol in Washington, Wednesday, March 13, 2019. (AP Photo/J. Scott Applewhite) Associated Press

And the numbers may bear out this belief.

For the president to be removed from office after a Senate impeachment trial, 20 Republicans must join the 45 Senate Democrats and 2 Independents to meet the 67 vote threshold for removal to take place.

Axios has identified only eight Republican senators, including Romney but not including Graham, whose vote may be in the balance. Most of them face re-election battles in 2020.

Graham's possible defection could be much more worrying for Trump, as it may encourage other Republicans privately critical of the president but publicly supportive to break cover and vote to remove him from office.

However, such a shift seems unlikely straight away, as Graham made a point of praising the president's domestic agenda in his Axios interview.

Meaning that though signs of weakness have appeared, the wall at this point still stands.