So how can you gerrymander Senate maps? Senators are elected on a state-wide basis.
This is a good time to note that there are many Democratic states such as Maryland, Connecticut, New Hampshire, Nevada, Oregon, California, Illinois, Massachusetts and others that are gerrymandered -- yet you conveniently ignore this reality.
Democrats Hate Gerrymandering—Except When They Get to Do It
In Maryland, New Mexico, and elsewhere, Democrats are just as guilty as the Republicans are in other states—which tells us that the real problem is deeper.
https://www.thedailybeast.com/democrats-hate-gerrymanderingexcept-when-they-get-to-do-it
https://www.wired.com/story/elections-2018-extreme-gerrymandering-blue-wave/
EXTREME GERRYMANDERING COULD STILL STYMIE THE BLUE WAVE
If you look at the polls and the forecasts put out by election oracles like Nate Silver, the race to win control of the House of Representatives on Tuesday seems tilted in Democrats’ favor. Michael Li will tell you that if Democrats do take back the House, it will have been against all odds.
In a report released earlier this year, Li and his colleagues at the Brennan Center for Justice found that in order to win a bare majority in the House, Democrats would need to win the national popular vote by 11 points, a margin no party has seen in decades. That’s thanks to gerrymandering, the process of strategically manipulating an election map’s boundaries to preference one political party or group over another. Since 2012, the country’s electoral map has been so heavily skewed toward Republicans that in severely gerrymandered states like Ohio, North Carolina, and Michigan, Democrats could win more than half the vote and still walk away with a minority of congressional seats