ANALYSIS: Trump's lived by the ratings but the numbers aren't working

— -- Three numbers to watch: President Donald Trump’s approval ratings and the percentage of Democratic votes in two special elections coming up soon. More than anything else those numbers will determine what Republicans on Capitol Hill do in dealing with their own investigations and the one former FBI chief Robert Mueller will now conduct.

As Trump whined “witch hunt,” complaining about the naming of a special counsel to investigate Russian interference in the U.S. election, Mueller received high praise from relieved Republicans. No longer will they be hounded by the public and the press demanding to know what they think about an independent investigation.

And, somewhat surprisingly, instead of trying to shunt the entire inquiry down Pennsylvania Avenue to the Justice Department, the Republican leaders also confirmed their support for the ongoing congressional inquiries. No one is circling the wagons around the president.

That’s because they are not afraid of him.

Despite the continued strong support from his voters, Trump’s overall approval rating hit 38 percent Wednesday, according to Gallup's daily poll. That’s lower than President Richard Nixon scored on the day the Watergate Special Committee first met, the same May day in 1973 that a special prosecutor was named.

By that point, two of Nixon’s campaign cronies had been convicted of burglary, wiretapping and conspiracy in the Watergate break-in; his two top aides had been forced to resign and he had fired his lawyer. But the public gave him higher marks than they currently assign to Trump.

As the Watergate investigations inexorably revealed more and more damaging information, including, finally, the proof of obstruction of justice on the Oval Office tapes, and his approval ratings sunk to the low 30s, Republicans pressed Nixon to resign. Even the party chairman, George H.W. Bush, privately told the president he had to go.

Compare that with what happened to President Bill Clinton after the Monica Lewinsky scandal stunned his party. Democrats privately assumed the president would not survive and some of Vice President Al Gore’s friends expected to see him soon in the Oval Office.

But the public had another idea. Buoyed by a booming economy, Clinton continued to earn approval numbers in the high 50s to low 60s and his critics backed off, allowing him not only to complete his term but to do it with the resounding approval of two-thirds of the electorate.

Trump has never come close to numbers like that -- and these investigations are likely to send his approval ratings lower.

If it turns out that Democratic candidates running in red districts in two special elections are the beneficiaries of Trump’s troubles, even if they don’t win but come close, then Republicans on Capitol Hill could cut the president loose.

No wonder Trump is raging about a “witch hunt.” He knows where this could lead.

Cokie Roberts is a political commentator for ABC News. Opinions expressed in this column do not necessarily reflect the views of ABC News.