It is readily apparent to most Americans that President Joe Biden, due in large part to his advanced age and declining physical and mental health, is struggling to effectively govern the country, much less campaign for a second four-year term in office.

Those struggles for the president have essentially been confirmed by his campaign's increasing reliance upon the first lady, Dr. Jill Biden, to hit the road on her husband's behalf, as she is doing this week with a planned trip to Phoenix, Arizona, according to local ABC affiliate KNXV.

Campaigning on behalf of the president

Though final details on the location and time of the visit have not yet been revealed, the first lady is expected to travel to the Phoenix area in the crucial swing state of Arizona on Friday for an Educators for Biden-Harris event.

The purpose of that event is to mobilize support for President Biden among teachers, school administrators and faculty, and parents.

It is part of a broader mini-campaign launched a few weeks ago by the first lady, according to an ABC News report at the time, that aims to portray the incumbent Democrat as "the education president."

Jill Biden has already visited states like Minnesota, Michigan, Nevada, and New Hampshire as part of the campaign within a campaign, and similar Educators for Biden-Harris events are planned for all of the important battleground states that so often decide close elections.

Perhaps unsurprisingly, given their overt partisan leanings, both major teachers' unions -- the American Federation of Teachers and the National Education Association -- have not only expressed their support for the effort but have also become actively involved in helping to garner support for President Biden.

First lady is Biden campaign's "secret weapon"

Politico reported in February that President Biden's re-election campaign viewed the first lady as their "secret weapon" and an asset to be deployed strategically as his "most effective surrogate" to help the incumbent Democrat win a second term in office.

The campaign praised her "fundraising prowess" among Democratic donors and purported ability to connect with voters, and the article highlighted the "rigorous schedule of traveling to swing states" she had already engaged in and planned to do going forward -- as she did ahead of the 2022 midterm elections and, to a lesser extent because of the pandemic, during the 2020 election cycle.

To be sure, the Biden campaign asserted that the first lady would be relied upon because of how busy the president is in dealing with developing crises around the world and the day-to-day business of managing the country from the White House in Washington D.C. -- but there is likely another major reason that they aren't openly admitting ... that Biden simply isn't up to the task of a grueling re-election campaign.

Most voters think Biden is too old and lacks the physical/mental fitness for the job

There is no denying that President Biden's age, 81, and his apparent decline in physical health and cognitive capabilities are legitimate worries for his campaign, whether they want to acknowledge that or not.

An NBC News poll in February found that a combined 76% of voters had "major" or "moderate" concerns about Biden "not having the necessary mental and physical health to be president for a second term" -- a figure that included 54% of Democratic voters.

More recently, Pew Research revealed last month that 62% of voters had no confidence in Biden's mental fitness to be president while 66% lacked any confidence that he had the physical fitness necessary for the job.

Notably, both of those polls showed that vastly fewer voters had similar age and fitness concerns about former President Donald Trump -- hence the Biden campaign's decision to limit the president's campaigning and make use of surrogates like the first lady to hit the arduous campaign trail on his behalf.