The initiation of an impeachment investigation against a president ought to be an earthshaking moment in the nation's history.

Yet when Republican House Speaker Kevin McCarthy announced the opening of such a probe into President Joe Biden Tuesday, it felt like more of an inevitable consequence of America's diseased politics than a constitutional thunderclap.

McCarthy argued that the impeachment inquiry was the "logical" next step amid Republican claims -- so far unproven -- that Biden was enriched by his son Hunter's business ventures when he was vice president. Impeachment did seem to be a logical next step -- but less from an evidentiary perspective than a political one, with the effort pushed by hardline Republicans, including many members who voted not to certify Biden's 2020 victory. The House GOP majority, which has remained in thrall to Trump, now serves as an arm of his bid to win back the White House next year.

The speaker's impeachment move comes as he is facing extreme pressure from far-right pro-Trump members of his conference ahead of an internal GOP showdown over spending and amid questions over whether he could survive as speaker if he fails to impeach Biden, following the double impeachment of his predecessor.

The impression that McCarthy is acting at the behest of a vengeful Trump was bolstered by the disclosure that the ex-president was on the phone with House leadership on Tuesday, as CNN reported.

It's not new for the California Republican to be seen to be Trump's proxy. He pledged loyalty to the former president at Mar-a-Lago days after he left office in disgrace for telling his supporters to "fight like hell" before the Capitol insurrection on January 6, 2021.

Republicans could use an impeachment investigation of the president to fuel public suspicion over Hunter Biden's cascading controversies. They'll try to muddle the political effect of Trump's own two impeachments and his four looming criminal trials by creating the impression that political corruption is simply endemic.

The United States is now on the cusp of its third possible impeachment in three and a half years. McCarthy's move raises the question of whether the standard for this last-resort constitutional remedy is being watered down. A new impeachment process that comes to be seen as purely politically motivated also raises the risk that a once-rare step will become a regular habit when the House is controlled by one party and the White House by another.

But the coming impeachment investigation represents a gamble for Republicans since it could cause a backlash in moderate districts that their majority depends on. And heading into 2024, when polls show limited enthusiasm for Joe Biden's reelection bid even amid in his own party, an impeachment inquiry into the president may help the White House boost excitement among Democrats. Ian Sams, a White House spokesman for oversight and investigations, blasted the impeachment investigation as "extreme politics at its worst."

But the strain of an impeachment inquiry is hardly the way the White House would have preferred to prepare for election year. The White House plans to send a letter to top US news executives on Wednesday, urging the media to "ramp up its scrutiny of House Republicans for opening an impeachment inquiry based on lies," according to a draft copy obtained by CNN.

Even if nothing comes of the inquiry, the chatter could increase voter concern about the president's role in Hunter Biden's affairs after 61% of the public said in a CNN poll released last week that they think he had at least some involvement in his son's business career.

And McCarthy's announcement came as concern mounts among some Democrats about Biden's age -- he would turn 82 before being inaugurated for a second term. In a column likely to drive conversation on the issue on Wednesday, influential Washington Post foreign policy writer David Ignatius, who is often sympathetic to the president, said he didn't think Biden and Vice President Kamala Harris should run for reelection.

Democratic Sen. Dick Durbin told CNN Tuesday that while the impeachment inquiry decision was a symptom of an "out of control" Republican House majority -- and that there was no evidence to back impeachment -- he did feel "uncomfortable" with the impression that Hunter Biden capitalized on his father's position, as he did about similar allegations about Trump's son-in-law, Jared Kushner, in the previous administration.

Suspicions of influence peddling by a son, but no evidence of presidential wrongdoing

McCarthy did not cite any evidence of wrongdoing by Joe Biden when he made the announcement of an impeachment inquiry. And he did not put the decision to a vote of the full House -- as he once said he would and for which he once criticized then-Speaker Nancy Pelosi for not doing -- amid signs that more moderate Republicans critical to his hopes of keeping the majority fear they could pay a price for the move in 2024.

"These are allegations of abuse of power, obstruction and corruption," the California Republican said, in announcing the investigation. "They warrant further investigation by the House of Representatives."

Information made public by GOP-led House committees suggests at the very least a strong perception of a conflict of interest on the part of Hunter Biden in various ventures, including in China and Ukraine, while his father was dealing with those foreign policy portfolios as vice president.

But despite releasing details of bank records connected to the younger Biden showing a series of lucrative payments, GOP House committees have failed to produce evidence that the president personally benefited from his son's business deals or that he abused his power in a way that would fit the constitutional standard for impeachment of treason, bribery and high crimes and misdemeanors. The Republican leadership of the House Oversight Committee claims that dinners Joe Biden attended with his son and his associates in 2014 and 2015 and a visit he made to Ukraine, shortly after Hunter Biden started earning $1 million a year from the Ukrainian energy firm Burisma, show corruption.

Yet those details don't seem to meet even the standard of circumstantial evidence showing that the president did something wrong. If the impeachment investigation does uncover more direct involvement of Joe Biden, condemnations of McCarthy's action may have been premature.

But until then, the speaker will be criticized for showing only questionable justifications for initiating a process that, if pushed to its conclusion, would result in a Senate trial of the president to decide whether the result of a democratic election should be overturned and he should be dismissed.

Impeachment is always an inherently political process

One of the complexities of impeachment is that the standard for judging whether a president has abused his power is not a criminal one -- it is a political question. One of the founders, Alexander Hamilton, for instance, wrote in Federalist 65 that prosecuting impeachments would "seldom fail to agitate the passions of the whole community, and to divide it into parties more or less friendly or inimical to the accused." He added: "There will always be the greatest danger that the decision will be regulated more by the comparative strength of parties, than by the real demonstrations of innocence or guilt."

In justifying his decision, McCarthy argued that an impeachment inquiry could unlock investigative powers not available to his majority in the normal course of business. But it is not clear that this is true. And absent stronger evidence of presidential wrongdoing at the outset, it's harder for him to rebut accusations that he's a weak speaker acting to save his own political skin. His tenure so far has been a procession of concessions to hardline "Make America Great Again" conservatives as he struggles to govern -- and the impeachment bid seems to fit this pattern.

Some observers have suggested that the investigation could buy the speaker space to escape a standoff with the right over spending that could shut down the government. But it's not a given McCarthy could appease members that way. And his warning on Tuesday that an impeachment inquiry doesn't necessarily translate to an actual impeachment seems difficult to take seriously since he'd have to face down pro-Trump lawmakers to halt it once it gathers momentum, even if it fails to unearth missteps by Joe Biden. One of McCarthy's fiercest critics, Florida Rep. Matt Gaetz, for instance, dismissed Tuesday's announcement as "baby steps."

By comparison with modern impeachments, the Biden investigation appears at the outset to be based on a thin foundation. President Bill Clinton was impeached for lying under oath and obstruction of justice after trying to cover up a sexual relationship with a White House intern, Monica Lewinsky. Trump's first impeachment was over abuse of power and obstruction of Congress after he tried to coerce Ukraine into a criminal investigation of Biden. His second was for "incitement of insurrection" after the January 6 attack on Congress. Clinton and Trump were both acquitted in Senate trials in the absence of a two-thirds majority to convict them. Lawmakers drew up articles of impeachment against President Richard Nixon amid the Watergate scandal in the 1970s, but he resigned before the full House could act.

David Bateman, a professor of government and policy at Cornell University, said the Clinton and Trump impeachments all appeared plausible. "They seem to be clearly offenses for which you should be impeachable," Bateman said. "This one right now, there's been no evidence produced that suggests there was anything other than a son who's trying to engage in some influence pending .... (And) no evidence that the father, as vice president, participated in any substantive way."

GOP presidential candidate Chris Christie, a Trump critic, warned in an interview with CNN's Jake Tapper that the paucity of current evidence against Biden augured against impeachment. "If in fact, you don't have greater facts than what you have now, it would be cheapening impeachment," the former New Jersey governor said, though he did add that "there is enough smoke here that you need to look."

The opening of an impeachment inquiry could cause uncomfortable questions for Republicans who represent districts that Biden carried in 2020. But McCarthy's decision not to put the issue to a vote in the full House right now could give some of these lawmakers cover. Rep. Dan Newhouse of Washington state, one of 10 House Republicans who voted to impeach Trump the second time around, echoed the party line when he said opening an impeachment investigation into Biden was the "next logical step."

But McCarthy's move on Tuesday seems to contradict his own claim to the moral high ground before the House voted to impeach Trump the first time in December 2019. He complained at the time that the move, led by Pelosi, was not supported by evidence. "Will we let impeachment become an exercise of raw political power, regardless if it damages our country?" McCarthy asked. "Or will we protect the proper grounds and process for impeachment now and in the future?"

"They want to undo the results of the last election, to influence the next one," McCarthy said at the time -- a comment that, in retrospect, appears to explain the pro-Trump GOP's behavior nearly four years later.

Unless an impeachment investigation uncovers some currently unforeseeable abuse of power by Biden, it is certain, given the Democratic control of the Senate, that there will not be a two-thirds majority to convict him in a trial.

As McCarthy said, when referring to Trump in 2019, "He is president today. He will be president tomorrow. And he will be president when this impeachment is over."

The key question, therefore, may not be whether Biden survives impeachment with his job intact, but whether McCarthy does.