The committee needs to do more than simply gratify Democratic desires to unearth factoids that they can spin into blaming Trump for trying to, at worst, stage a coup. It needs to investigate energetically all potential causes, primary and secondary, for what happened. It also needs to allow people who strongly disagree with its initial premise to participate precisely so that they have the opportunity to throw the investigation off its course. Only by doing both of those things will the committee have a strong case that will withstand the inevitable partisan assaults from Trump’s die-hard defenders.
Republican consent to the committee’s findings is not necessary for them to be seen as credible, but Republican participation is. Imagine if the Watergate committees tasked with investigating President Richard M. Nixon’s crimes had excluded the Republican members who were defending the president. Those committees changed public opinion because those defenders, despite their best efforts, could not credibly argue against what the committee unearthed. Nixon began his second term in January 1973 with a 68 percent Gallup approval rating, but by August 1974, 57 percent of Americans believed he should be removed from office. That could not have happened without the active participation of members who were viscerally opposed to the investigation from the beginning.
Without Republican appointees being able to freely participate in the Jan. 6 committee, we are almost guaranteed that we will not find out the full truth.