Remember, the St Paul history of the Rondo neighborhood being destroyed because the government wanted to build a freeway. In the world according to Senile McCain, that was unconstitutional, because McCain said in a speech, noted by both a DailyKOS person listening to CNN and also the Wall Street Journal:

There is a very clear standard in the Constitution requiring not only just compensation in the use of eminent domain, but also that private property may NOT be taken for "public use."
(NWTerriD at DailyKOS)

Both articles also note the other mistakes made in the same speech:

While the speech as written went far to allay conservatives’ concerns, McCain appeared off his game as he delivered it. He said he appreciated the “hospitality of the students and faculty of West Virginia” before immediately correcting himself and saying “Wake Forest.”

He also stumbled over several passages, sometimes changing the meaning of the thought altogether. For example, his prepared remarks read: “There is a very clear standard in the Constitution requiring not only just compensation in the use of eminent domain, but also that private property may be taken only for ‘public use.’” But when McCain delivered the comments, he added “not” – as in “may not be taken only for ‘public use.’
(Wall Street Journal)

This is not the first time that McCain has demonstrated a pattern of confusion. Note that previously, McCain had mixed up Sunni and Shiite groups in Iraq:

Mr. McCain said several times during his visit to Jordan – during a news conference and a radio interview — that he was concerned that Iran was training members of Al Qaeda in Iraq. The United States believes that Iran, a Shiite country, has been training and financing Shiite extremists in Iraq, but not Al Qaeda, which is a Sunni insurgent group.
(New York Times)

Indeed McCain's performance at Republican debates has been mocked by Republicans, for example in this video clip on his answers about the economy. In this clip, he adovcates zero interest rates. No kidding. Zero interest rates is like handing out free money to everyone. Basically Germany tried printing excessive money to pay national loans, it was a total economic diasaster.

So we have strong evidence of McCain being senile. As a senator, a person has time to think and ponder, has the time to react slowly. However, a president has to react quickly and has to process complex and changing situations. The reaction to Hurricane Katrina is an example of already very slow Republican leadership in crisis. A president ought to be the most capable of leaders, not handicapped by senility. It seems strange that we would have a president who will be 75 years of age, when we require air traffic controllers to retire at 56.

Mandatory retirement age rules still prevail in some private and public-sector occupations: State and local police (55-60) and firefighters (55-60); federal firefighters (57); federal law enforcement and corrections officers (57); and air traffic controllers (56, if hired after 1972); and commercial airline pilots (60).
(MedRounds)

One might argue that a president doesn't require doing what an air traffic controller does, which according to studies the abilities are "ability to prioritize, situational awareness, planning, execution, thinking ahead, short-term memory, reasoning, decisiveness, concentration, perceptual speed and accuracy, mathematical reasoning, and ability to deal with dynamic visual movement." It seems to me, that except for the ability to deal with dynamic visual movement, all of the rest applies. Here is the abstract of the study:

Abstract : Researchers have explored the issue of air traffic control specialist (ATCS) age and performance many times over the past few decades. These researchers have consistently found a negative relationship between the age of Air ATCSs and both training success and ratings of job performance. A recent study (Heil, 1999) found a curvilinear relationship between ATCS age and performance on a computerized simulation of air traffic situations, with performance decreasing for people in their mid 40s. Some researchers (Heil, 1999; Schroeder, Broach, & Farmer, 1997) have speculated that these relationships maybe due to a decline in cognitive ability with age. The purpose of the current study is to investigate the relationship between age and performance on tests of cognitive ability for incumbent ATCSs. As part of a concurrent validation study, 1083 incumbent ATCSs from 12 enroute centers took a newly developed air traffic control selection test. The tests included in the 6 hour battery were developed to measure the knowledge, skills, abilities, and other characteristics (KSAOs) relevant to the ATCS job. Some of the KSAOs measured by the battery include: ability to prioritize, situational awareness, planning, execution, thinking ahead, short-term memory, reasoning, decisiveness, concentration, perceptual speed and accuracy, mathematical reasoning, and ability to deal with dynamic visual movement. The relationship between current age and performance on these cognitive tests was compared using regression analysis and analysis of variance procedures. The results of these analyses suggest some age-related decline in those cognitive abilities that are most important to successful job performance.
(Emphasis mine - Federal Aviation Administration)

Studies comparing driving and aging also show the effect of aging on cognitive abilities:

On a per-mile basis, elderly drivers have a higher accident rate than other drivers... Aging has a definite effect on driving ability. Changes first begin to occur in basic sensory and cognitive functions. These changes are so gradual older adults are unaware of them. These age-related problems can significantly affect an individual's driving performance.
(Emphasis is mine - MedRounds)

Neurobiology of Aging Information Center describes aging effects as showing up noticably after 70. McCain is now 71 and will be 75 when he leaves office.

Cognition refers to mental processes used for perceiving, remembering, and thinking. Most studies show that, in general, cognitive abilities are the greatest when people are in their 30s and 40s. Cognitive abilities stay about the same until the late 50s or early 60s, at which point they begin to decline, but to only a small degree. The effects of cognitive changes are not usually noticed until the 70s and beyond.
(American Federation for Aging Research)

Even as the article tries to play down the effects of aging, it still says that

However, complex tasks that require taking in new information and analyzing it may become more difficult. Many researchers attribute this to deficits that occur in attention, speed of processing, and memory.
(American Federation for Aging Research)

In a job as important as the president of the United States, with the responsibility of making decisions in the possible lighting fast decisions of nuclear war responses, should we not ask for the very best of decision makers?