WASHINGTON Hes too old. He rambles and makes no sense. There are legitimate concerns about his mental and physical fitness to be president.

But Donald Trump, 78, didnt raise much concern among Republicans this week when, during a campaign rally , he incoherently wandered through his remarks, went off on a bizarre tangent about a beautiful waitress and attacked a former political adversary as a fat pig.

Did you ever hear of Hannibal Lecter? Trump said at one point , comparing the fictitious cannibal to people who are allegedly coming to the United States from psychiatric wards.

The alarming display by the GOP presidential hopeful certainly raises questions about his ability to potentially lead the country should he win the election in November. Hes already raising serious concerns over his stated plans as president for another four years.

But it is President Joe Biden who continues to face intense scrutiny about his fitness for office, with at least a dozen congressional Democrats openly calling for him to step aside for a younger presidential nominee. Dozens of other Democratic lawmakers are privately expressing concerns about Biden following his disastrous performance in last months presidential debate.

Republicans on Capitol Hill arent asking the same questions about their nominee. On the contrary, they say that Trump is perfectly fit and mentally stable to serve in the White House.

Its just about ability, Sen. Marco Rubio (R-Fla.), 53, said Thursday. I mean, I know people that are younger than me that I wouldnt want to be president. And I know people almost twice my age that could run circles around most people around here. So its not an age thing as much as it is mental acuity and the energy and the focus.

Rubio, who has been mentioned as Trumps possible vice presidential pick, said the 78-year-old seems totally up for the job of president again because the guy is awake at 12 midnight and hes awake at six and five in the morning.

Sen. Bill Cassidy (R-La.), who is a doctor, said he thinks there is a biological difference between the two men.

Theres a physiological age and theres a chronological age, and theres not always a comparison, right? Cassidy told HuffPost. Its unfair [for] people of any age to assume that everybody at the same age is exactly the same. If you ask any woman if a man of 25 is as mature as a woman of 25, what do you think the womans going to say?

The point is that there are differences even for people at the same age, he concluded.

Trump was known for keeping a light schedule by the tail end of his presidency. He often didnt show up to work until near midday, with plenty of off-hours in his schedule, which White House staff billed as his Executive Time . More recently, during his criminal hush money trial in May, Trump often had trouble keeping his eyes open, appearing to doze off in court on multiple days.

Several former Trump aides have questioned his mental acuity and declared him unfit for office, including former chief of staff John Kelly, former Chairman of the Joint Chiefs of Staff Mark Milley and some members of Trumps Cabinet. They collectively said he lacks the temperament, values and character to be president, and cited actions he took while in office, the least of which was seeking to overturn an election he lost, which culminated in the Jan. 6, 2021, insurrection.

Mr. Trump has shown a character unworthy of the responsibilities of the presidency. He has demonstrated an utter lack of respect for the Constitution, the rule of law and the American people, wrote the editorial board of The New York Times , which also called on Biden to step aside, on Thursday, declaring Trump unfit for the presidency.

Instead of a cogent vision for the countrys future, Mr. Trump is animated by a thirst for political power: to use the levers of government to advance his interests, satisfy his impulses and exact retribution against those who he thinks have wronged him, they wrote.

To Republicans on Capitol Hill, however, Trump is a lock for the presidency, especially now that Biden is facing an open rebellion within his party (voters perceived Bidens age as a far greater liability even before the debate).

For all his ills, a Trump win in November could deliver the GOP total control of Congress and the White House, unlocking a path for their conservative agenda, including another round of tax cuts and possibly even more seats on the Supreme Court.

And Republicans say Trump simply looked better on the debate stage standing next to Biden in Atlanta last month.

Hes got a lot of energy, Sen. John Cornyn (R-Texas), 72, said Thursday. He seems as sharp as he ever was. Lets face it, not all 78-year-olds or all 81-year-olds are the same. I think President Biden is obviously experiencing some challenges that I dont see in President Trump.

Not all GOP lawmakers were quick to draw sharp differences between Biden and Trump, though.

Sen. Lisa Murkowski (R-Alaska), a Trump critic, noted that they are the two oldest major party candidates to seek the U.S. presidency.

Theyre both two older white men, Murkowski said.

Some Democrats have emphasized its worth highlighting the major differences between the two that have little to do with age.

One has a record you can be proud of, the other has a record you dont want to talk to your mom about, Sen. John Fetterman (D-Pa.), a staunch Biden supporter, said Thursday on The View. One, youd be proud to shake his hand. The other, youd wonder where that hands been.