I suggest you review the constitutional powers of Congress over the judicial branch - “BEFORE putting mouth into gear.”
In theory, a Congressman could “take on” voting fraud.
I suppose they could make a speech or something (that the media would not broadcast). Maybe they could hold a hearing, which the media would not broadcast (and for which Republican leadership might strip them of their chairmanship or assignment). Republican leadership, which consented to this decree in 1982, has shown no tolerance of serious attempts (legislation) to address it, even when they held both houses and the Presidency under Bush 43.
In practice, it takes a lot of people on the ground to prevent (or substantially enact) voter fraud. They have to be organized and trained - it is a long term sustained effort. The Democrats have a variety of such groups, the Republicans do not, coordinated through their national committees. This is the REALITY, and has been for decades.
Get real.
Believing it is impossible, is living in an alternate reality.
I fail to see how “the constitutional powers of Congress over the judicial branch” has any effect. It does not allow Congress to make or overturn court decisions. They just establish courts. The ruling in question was a consent decree anyway (RNC consented to it).