Do the Democrats need their own Tea Party? If one intransigent movement in Congress can create so many problems from the right, imagine what life in Washington would be like if its mirror image emerges from the left. But that seems to be the direction we’re headed.

In last week’s column I discussed the possibility that President Trump, having been raked over the coals by the conservatives in the House Freedom Caucus during the recent health care debate, might now turn to the Democrats as potential partners on taxes, infrastructure and his other domestic policy goals. But even if Trump does extend his hand across the aisle, it appears likely that no one on the other side would be willing to accept it.

Since the election, grassroots Democrats have made it clear to their elected leaders that they are in no mood to try to find common ground with the president. When Sen. Chuck Schumer, D-N.Y., suggested after the election that it might be possible to work with Trump on certain issues, he was quickly slapped down by his followers. Democratic senators who voted for Trump’s Cabinet nominees were called out as traitors and heretics, and a movement has already begun to deny party funding for the re-election campaigns of the three Democrats who supported Neil Gorsuch’s nomination to the Supreme Court.

Most smart Democrats know that relying solely on the passion of progressives is a dangerous game, and that driving away the party’s remaining moderate voices is a recipe for disaster. But most of them are reluctant to speak up and face the wrath of their party’s base.

Enter Kamala Harris.

California’s new U.S. senator possesses the agenda, the biography and the attitude to make the hearts of most progressive activists skip a beat. Harris won her election last fall running hard from the left and much of her work since arriving in Washington is more likely to excite Democratic loyalists than it is to appeal to more centrist voters. But there she was last week arguing that her party could not afford to abandon its colleagues who had voted for Gorsuch.

“We can’t afford to be purists,” Harris said. “Can you understand that you may not agree with 50 percent of their policy positions, but I can guarantee you will disagree with 100 percent of their replacements’ policy positions. So that is part of the question. What do we have to do in this movement to be pragmatic?”

Strong stuff, and almost certainly not what her supporters would like to hear from her. But even though pragmatism is not going to be a particularly effective rallying cry for Democratic loyalists anytime soon, Harris is giving them the right advice.

The grassroots activism among progressives is similar to the populist uprising that emerged among conservative resisters during the first months of Barack Obama’s presidency eight years ago — right down to the combative nature of last week’s congressional town hall meetings. The unexpectedly narrow victory for the GOP candidate in an overwhelmingly Republican House district in Kansas last week further demonstrates that the fire and energy now is emanating from the left end of the political spectrum. All in all, 2017 is beginning to feel like 2009 in reverse, as a wave of angry opposition emerges against a newly-elected president still learning the ways of Washington.

Democrats understand that the Obama years were very beneficial for conservatives in many ways. An ultra-motivated insurgency brought Republican majorities in both houses of Congress as well as sizable gains in governors’ offices and statehouses across the country. There is no shortage of liberal activists and donors who believe they can achieve the same sweeping victories on the wings of equally passionate and uncompromising activists.

Impassioned Democrats believe that Trump will be such an ineffectual president and such a weak candidate by 2020 that simply turning out their base will be good enough to reclaim the presidency. (Which was precisely the attitude that equally impassioned Republicans held toward Obama before he was re-elected.) But a political party that consciously ignores the political center is not leaving itself much margin for error.

Ronald Reagan once warned his most impassioned allies of the dangers of “jumping off the cliff with the flag flying.” Harris is unlikely to quote the conservative Californian by name to her fans. But Reagan was right then, and so is Harris now.

Dan Schnur, who has worked on four presidential and three gubernatorial campaigns, teaches political communications at the University of Southern California and UC Berkeley. To comment, submit your letter to the editor at http://bit.ly/SFChronicleletters.com