The Justice Department's Nov 2 release carries two numbers side by side: "In the last nine weeks alone, the Department has charged 195 aliens across 25 states," and "Since the beginning of this Administration, we have charged 239 people."
Divide one by the other and 81.59 percent of the cases fall in the nine weeks before the Nov 3 midterm. The two figures use different nouns, aliens and people, so the share is approximate.
The release went out at 4:09 p.m. Eastern the day before the vote, with Attorney General Todd Blanche calling it "the largest surge of voter-fraud arrests since President Trump returned to office." A week earlier, DOJ's Oct 26 release repeated all 28 California defendants first announced on Oct 19. Whether the 195 and 239 totals count those 28 twice is not stated.
The pace could reflect when investigations matured or a stated enforcement priority; DOJ's pages give no reason for the timing. All defendants are presumed innocent until proven guilty.