A bipartisan majority of the U.S. Senate voted that it’s constitutional to impeach a former president. This was consistent with precedent established in prior impeachments. A large majority of the constitutional scholars, including many well-respected conservatives, agreed.
The vote also adds weight to possible future impeachments. Hypothetically, if President Biden commits impeachable acts so late in his term that proceedings couldn't be concluded prior his leaving office, Congress would properly rely, at least in part, on the recent vote as supporting impeachment.
Members of both parties would almost certainly treat the issue of constitutionality as resolved.
If constitutionality would be a non-issue in the future, based on this precedent, why have some senators continued to lean on asserted unconstitutionality in this year’s impeachment proceedings? Is this simply an excuse to avoid having to vote on the actual merits of the case?
In February 1968, Martin Luther King Jr. observed: "On some positions cowardice asks the question, is it safe? Expediency asks the question, is it politic? Vanity asks the question, is it popular? But conscience asks the question, is it right?"
Look at our senators’ votes, and judge for yourself which considerations appear to govern their decisions.