There have been questions about a number of elections. 2000 was the most recent.
The election of 2000 is no longer (in the reality based world) controversial - Gore took Florida and won the electoral as well as popular vote, the Supreme Court debased itself by taking a Partisan side - both tactically (in scheduling etc) and ideologically (in over-ruling a valid and legitimate Florida Court decision).
On the topic of "packing": We are looking at the confirmation of the third Supreme Court Justice who worked for the Republican Party in that one now universally derided 2000 legal mess - the Partisan legal team from that one Partisan and legally dubious case (people have suggested disbarring some of the lawyers involved) has staffed a third of the United States Supreme Court.
2004 and 2016 were also reversible on the evidence (2016 certainly, 2004 probable) if accurately counted and vote suppression prosecuted. (Kerry probably "wins" the electoral vote, Clinton pretty much landslides - the popular vote by 4 or 5 million, the electoral college reflecting that.)
That's nationally, a cumulative product of the individual Republican-governed States suppressing the vote under a variety of dishonest pretensions, threats, and bribes. It is one of the ordinary and characteristic features of fascist government - the necessity of holding an election as part of the theater of legitimacy, the necessity of preventing an election from registering the majority will or allowing it access to power
(fascist governance being by consequence and physical necessity governance by a minority faction - parasitic, therefore smaller, like all criminal famil
ias).
At my State level the holding and vetting of reasonably, statistically, and apparently, honest elections has been routine since WWII at the latest. Since US elections are run by the States, any other State could imitate this one (Minnesota) or another of the more honest ones - they would need to replace their current administrations with non-Republicans, of course.
It's the counting, not the voting, that identifies democratic representative governance.