Except gas prices were high before the Ukraine issue, and as I understand it, there haven't been any sanctions on Russian oil yet (could be wrong about this). Gas price could very well be a bit lower than they are at this very moment, but Biden is going to have start removing at least some of the restraints on US Energy if he wants price to go back to what they were before he took office. Yes, Dems would be smart to do this before midterms, but they don't have a track record of making smart decisions, certainly not in Biden's term of office, so no reason to think they will now. Besides, it's unlikely they will win back a lot of voters, and perhaps alienate the far left wing.
Then again, Dems don't need to win elections, they just need to get into cheating distance. As well, Dems tend to get a lot done when they are not in power. At the very least, they can generate enough hate for Republicans and conservatives that no one pays attention to how horrible they are.