No matter what you think of the idea, Tom Steyer's Need to Impeach campaign has brought the discussion of impeaching President Trump into the political mainstream. Steyer believed in late 2017 that there was more than enough evidence of obstruction of justice and violation of the Constitution's Emoluments Clause to impeach the President. Working with Putnam Partners, Steyer began airing a series of national television advertisements focused on raising the issue and making the case for impeachment.
Steyer's goal was to apply pressure to Democratic AND Republican congressional leaders to begin seriously considering impeachment proceedings in the face of a chaotic and deeply concerning presidency that is viewed as an existential threat to the country. The other principal goal was to begin airing advertising that addressed issues of great importance to the Democratic cause, such as opposition to the Republican tax reform plan.
The reality of the moment was that there were no organized efforts to mobilize public support for Democratic priorities other than candidate campaigns. The absence of issue-focused advertising by progressive groups and the national Democratic Party (while Republican efforts have been widespread and well funded by party groups and deep pocketed donors) has been an ongoing challenge for Democrats stretching back to the introduction of the Affordable Care Act. Republican opposition mounted a strong advertising campaign against "Obamacare," while there was no air cover making the case in favor of ACA. Steyer was determined to not let the same thing happen with President Trump's Tax Reform bill.
The campaign has successfully injected the topic of impeachment into the media mainstream with countless discussions on cable news and in major print media. It mobilized opposition to the Republican tax reform plan by being the only paid media campaign of any sort airing advertising against tax reform. As of January, 2018, it has gathered nearly five million signatures (and email addresses) of support for impeaching the President.