Impeachment is a lengthy process that upsets or turns off many people. Furthermore, it's dangerous to the people involved because it's fraught with many opportunities for missteps and overreach.
I think that Limbaugh thinks that the timing has passed for impeachment running into the next election, and the Democrats feel their best option is for a de facto impeachment at the ballot box in 2020.
Instead of impeachment proceedings, Democrats will focus on smearing Trump to make him toxic to voters in the next election. The test will be whether Republicans continue to play along or show some nerve and fight back. Anything the Democrats do to damage Trump will have down-ballot implications for all Republicans in the next election, so it's in their best interests to start supporting Trump against the upcoming Democrat Propaganda campaign.
-PJ
On reflection, you are correct about Rush.