The Trump Administration is so dreadful they've made the George W. Bush Administration seem almost acceptable in comparison. Dubya surrounded himself with qualified staff. As awful as Bush Vice President Dick Cheney was, he had notable Washington experience: he'd served as White House Chief of Staff and as Secretary of Defense. In contrast, Mike Pence went from conservative talk-show host to Ineffective congressman (and governor) to Trump's Vice President.
Nonetheless, the primary criticism of Pence isn't that he doesn't possess the cojones to perform the job of President, if need be. The Vice President -- who has touted his "Christian credentials" -- is castigated because he could act as a moral check on Trump. Instead, Pence has chosen to be Trump's primary cheerleader. His fawning buddy. His toady.
When Trump selected Pence as his running mate, none of us expected them to be equal partners in a Trump Administration; it was unrealistic to expect Pence to compliment Trump's imbecility with thoughtful insight. Most observers recognized Pence for what he was intended to be: an empty suit with impeccable conservative Christian credentials who had the blessing of Republican oligarchs such as the Koch brothers and Robert Mercer. (In July 2016, Trump was leaning towards choosing New Jersey Governor Chris Christie as his running mate; Trump Campaign Manager Kellyanne Conway persuaded Trump to choose Pence -- for the stated reasons plus the fact that Pence would be better as the liaison to congressional Republicans. By the way: Conway got her position because of the influence of Robert Mercer.)
Now, Pence has a limited portfolio within the Trump Administration: he placates big donors, such as the Koch brothers and Robert Mercer, and also reassures the religious right. (In July 2016, the 538 website noted that Pence was the most conservative Republican VP candidate in forty years (http://fivethirtyeight.com/features/mike-pence-would-be-a-really-conservative-and-mostly-unknown-vp-pick/ ).) When there's a Trump imbroglio, Pence declares fealty to Trump and the religious right is assuaged -- this first happened with the October 2016 release of the notorious Trump "Access Hollywood" tape and has continued to the present day with Pence's support for Trump in the Stormy Daniels scandal. (Uncharacteristically, on May 21st, Pence spoke out on North Korea, threatening it with "the Libya model." In response, a high-ranking North Korean official called Pence, "a political dummy," characterizing his remarks as "ignorant and stupid.")
Nonetheless, because of Pence's high-visibility Christianity, many political observers believed he would provide a moral framework for Trump; they expected that when Donald Trump became president he would soften his behavior and that Pence would play an important role in this process. That is, they expected Trump would begin to act presidential. This hasn't happened and part of blame must fall on the shoulders of Mike Pence.
In his May 9th Washington Post oped (https://www.washingtonpost.com/opinions/trump-is-no-longer-the-worst-person-in-government/2018/05/09/10e59eba-52f1-11e8-a551-5b648abe29ef_story.html? ), conservative columnist George Will criticized the Vice President: "The oleaginous Mike Pence, with his talent for toadyism and appetite for obsequiousness... is the authentic voice of today's lickspittle Republican Party, he clarifies this year's elections: Vote Republican to ratify groveling as governing." George Will noted that Pence frequently claims he is "deeply humbled" to be able to serve in the Trump Administration.
George Will castigated the President: "Trump is what he is, a floundering, inarticulate jumble of gnawing insecurities and not-at-all compensating vanities, which is pathetic." But Will savds his most ferocious commentary for the Vice-President: "Pence is what he has chosen to be, which is horrifying."
Why has Mike Pence become Trump's toady?
There are two possible explanations; neither of which is flattering to Pence. The first is that the Vice President has realized that the only way to work closely with Trump is to continually flatter him; that Trump is so insecure that he only will tolerate close relations with those who proffer their unwavering love. This suggests that Pence -- realizing that Trump threatens the United States -- has decide to dampen his personality and pander to Trump, believing that only this behavior will mollify him.
The second explanation is that Pence actually lacks a moral core; he is a hollow man ("Shape without form, shade without color, paralyzed force, gesture without motion", T.S. Eliot) The Vice President is not able to stand up to Trump because Pence is a weak person; he's playing a part in a political play and only reads the lines that he's been given -- he's been instructed to be Trump's toady and that's what he is doing.
Since Trump became President there have been calls for his impeachment. Many observers have warned that if Trump was removed from office, we'd get Pence as President and he would be worse.
What we know about Pence suggests that if he were to become President he would be different from Trump. Nowhere near as crazy. (No demented early morning tweets.) Pence would be a more conventional Republican President; an actor, content to read the lines written for him by Republican oligarchs. Instead of being Trump's toady, Pence would grovel at the feet of the powerful men who control the Republican Party.
Trump or Pence. Not an appealing choice.