In the vacuum of ideas that is today's Democratic Party, removing President Trump from office is the single unifying force among the Democrat base.  According to politico.com, "[p]olls on the question show as many as three-quarters of Democrats already back impeachment," even though "there is no consensus on the grounds" for impeachment. 

But fear of political backlash is "roiling" the Democrats as 2018 approaches:

The debate is roiling House Democrats, with progressives forcing a debate over the issue even as vulnerable incumbents, particularly members in districts that favored Trump, worry it could jeopardize their future in Congress.

Politico writers Kyle Cheney and Heather Caygle observe that while "Democratic hostility toward" Trump "seems to intensify daily," the impeachment debate is not helping the "12 Democrats" from districts "Trump won in 2016."

One such Democrat up for re-election says the recent impeachment vote "by 58 House Democrats" was "entirely unnecessary and hurtful to people in certain districts."

The more cautious Democrats are said to be "waiting for the outcome" of the "special prosecutor investigation" and hoping for "bipartisan buy-in" to impeachment, on whatever grounds.  A California Democrat House member "who supports impeaching Trump" says:

The bipartisan piece of it is assurance to the public that you're not just playing partisan games.

But the same Public Policy Poll linked in the Politico column says 85% of Hillary voters support impeachment and 86% of Trump voters oppose impeachment (page 18).  That sounds bipartisan.

The poll also says 88% of Hillary voters think Trump is "mentally unbalanced," while 86% of Trump voters think Trump is "mentally stable" (page 14).  No partisan games there.

New York Democrat Jerry Nadler, who was elected last week to be the ranking Democrat "on the House Judiciary Committee, the panel that handles impeachment matters," argues that "it makes little sense to pursue a partisan impeachment" when the result might be "stopped cold in the Senate."

But other Democrats have "no qualms about talking impeachment now," with "an animated base demanding the party's leaders use the full range of their powers to target Trump."

While the Republicans can run in 2018 on tax cuts and the booming Trump economy, the Democrats can run on overturning the last election to satisfy their animated base of resistance.

The Politico piece notes that the impeachment movement depends on "explicit evidence" of "collusion or obstruction" emerging from the Mueller investigation.  President Trump, however, knows that it really depends on the public's perception of the Democrats' game.

Demonstrating once again his mastery of branding, the president referred in a Tuesday tweet to the "bogus" "DNC funded Dossier" at the heart of the Mueller investigation:

And they used this Crooked Hillary pile of garbage as the basis for going after the Trump Campaign!

Whether or not John Q. Public knows what the dossier is or what Mueller is investigating, the president has not so subtly branded the entire proceedings as "this crooked Hillary pile of garbage."  In layman's language.

Just as President Trump may be standing aside as the Mueller investigation defeats itself, the Republicans might just stand aside and let the Democrats defeat themselves in 2018.