The Democrats took the House in two wave elections. The first, in 2006, was largely a reaction to the war in Iraq. The 2008 election was a reaction to the financial crisis. The Republicans formed the Tea Party in 2009 and took the House back the following year. Considering that the Democrats controlled the House for 58 out of 62 years then the House may be in a similar, long-term Republican period with short interruptions because of external events. If this is true then there is no pendulum to swing back.
It's instructive to look at what was going on when the House changed hands. 1994 was partly a reaction to Bill Clinton's presidency but it also featured the Contract With America - a set of issues that the Republicans promised to vote on in their first 100 days. They delivered on their Contract, also, but it was mainly symbolic since the Democrats still controlled the Senate.
The House is a different animal. The Democrats controlled it continuously from the 1930s until 1994 with the exception of the Republicans controlling it twice, both times for single term in the 1950s. The Republicans finally won control of the House in 1994 after 40 years and kept it until 2006 then won it back again in 2010.
But is it even rational to assume that 2018 will be a Democratic wave election? The White House changes parties regularly. Since World War II, it's switched every 8 years with two exceptions, both involving Reagan (Reagan defeated a sitting president and his successor was elected but only held the White House for a single term). The Senate has changed hands several times since the Republicans took it in 1980 but its shifts tend to take 6 years or longer. The Republicans have only controlled the Senate since 2014.
So any hopes of removing President Trump involve a lot of wishful thinking.
And, even if the Democrats did manage to remove Trump, that just elevates Pence to the presidency. Are we to believe that they will find cause to impeach him, too, so that nancy Pelosi can be president (it goes without saying that they will also refuse to confirm a replacement vice president after Trump is removed).
But, let's assume that the Democrats manage a clean sweep and win all 33 seats. That would give them 56 seats. Assuming that they also take the house and pass a bill on impeachment, then the Senate would have to vote on removing President Trump and that takes a 2/3s super-majority. They'd have to have 67 votes. Does anyone seriously think that 11 Republicans will join the Democrats in ejecting a Republican president? The best guide we have to go on was the impeachment of Bill Clinton which failed in the Senate because the Democrats refused to vote to remove him, even though there was no question that he was guilty of perjury.
Because Senators server six year terms, the people coming up for reelection in 2018 are the ones who last ran in 2012 with Barack Obama at the top of the ticket. The Democrats who won were riding on Obama's coattails and the Republicans who won were bucking a headwind. The numbers show that. The Democrats and independents who caucus with the Democrats are defending 25 seats. The Republicans are defending 8. That's long odds for the Democrats.
Ever since the election I've been seeing people on the left talking about how Trump will be president for two years. The highest profile version of this I've seen to date is a column by former conservative Kathleen Parker. She says:This is a total fantasy. There is no way that the Democrats can remove Trump from office, even in an unprecedented landslide. No chance at all.
My "good" prediction is based on the Law of the Pendulum. Enough Americans, including most independent voters, will be so ready to shed Donald Trump and his little shop of horrors that the 2018 midterm elections are all but certain to be a landslide — no, make that a mudslide — sweep of the House and Senate. If Republicans took both houses in a groundswell of the people's rejection of Obamacare, Democrats will take them back in a tsunami of protest.
There is good reason to believe this. The country in general tends to be center-right but in the last two decades people have self-selected so that the country is a sea of red with small clusters of urban-dwelling liberals. This makes it nearly impossible to draw competitive congressional districts. Ohio continues to be nearly 50/50 but the graphic below shows how the Democrats have retreated into only a few counties.
Even if we assume that it is possible to swing Congress back so soon, what will the Democrats' message be? Their post-election analysis rejected and moderation in favor of doubling down on progressive policies and identity politics. They have sworn to to all that they can to resist President Trump at every level. That satisfies their base but they already have the base's vote. A lot depends on how Trump's policies play out but the Democrats are taking a huge risk. They are convinced that Trump is a terrible president and that the rest of the country will eventually realize it. They have no plan B. If Trump succeeds or even muddles through then the Democrats will fail.