In a matter of 2 ½ months, the Democratic presidential field of candidates has changed their tune after initially embracing left-wing causes promoted by Sens. Bernie Sanders and Elizabeth Warren.

At last Thursday’s debate in Houston, the 10 participants turned down the volume on many of the “big, bold ideas” on immigration, racial issues and the environment that dominated the first debate in Miami in June and, to a lesser extent, the faceoff in Detroit in July.

Pundits and academics have reminded Democratic activists and strategists that the party veering too far left is a gift for Trump and the GOP. Worried party leaders and campaign donors have reinforced that view. Candidates know how to read polls and interpret research that shows moderate candidates typically come out of the primary season relatively unscathed and fare far better in the general election.

In fact, one study conducted at Stanford University found that an extremist congressional candidate nominated by either party in the primaries will typically fall seven points short in the general election compared to a moderate candidate. The party fronted by a firebrand is one-third- to one-half less likely to win in November.

Moderates win GOP-leaning seats, not liberals

The 2018 election, marked by Democrats retaking control of the House, tells the story. Nearly all the House seats that flipped from red to blue last year were won by moderates running in districts that favor Republicans. Liberals running in deeply Democratic territory were victorious in primary elections. Overall, 22 of the 30 freshmen moderates – members of the New Democrat coalition – prevailed in key districts that lean toward the GOP.

In the presidential race, though nearly all of the moderate candidates have exited the race or have been relegated to non-factor status, the tone of the contest has changed. Most of the remaining contenders seem focused on the idea that 2020 will be about fighting off Republican claims that Democrats are now the party of socialism. And they don’t want to give Trump and Co. the red meat to chew up their party.

At the time of the Miami debate, many of the roughly two dozen candidates embraced a series of ultraliberal ideas that are highly unpopular in polls: making illegal immigrants eligible for taxpayer-funded health insurance, decriminalizing illegal border crossings, disbanding the Immigration and Customs Enforcement (ICE) agency, and providing reparations to black families as compensation for slavery.

In Houston, only the proposed “Medicare for all” approach toward health care remained as an ultraliberal idea that the candidates were eager to debate. Essentially, Medicare for all is now a Sanders and Warren tenet, with the others expressing varying degrees of opposition of skepticism. Surveys show that voter support for that approach plummets when poll respondents are told that this system of national health insurance would entail tax increases and the elimination of private insurance.

Researchers have found that Democratic progressives who believe bold campaign proposals will energize the liberal base in 2020 are missing half of the equation. The data shows that approach tends to activate their opponent’s base even more than their own, resulting in a net loss on turnout. In other words, they may be playing right into Trump’s hands. Academics say those who go rogue, so to speak, also seem to lose to the opposition party those people who almost always turn out to vote, while moderate nominees hold on to those voters. In this way, the findings show, extreme nominees lose votes in two ways: “mobilization and persuasion.”

Centrism is not sexy

Sure, centrism is not sexy. Incrementalism and pragmatism do not rile the base. But Dems who want to retain control of the House and win the White House should concede that winning in the November 2020 general election means attracting mainstream Democrats and independents.

Consider this: the Dems’ new House majority consists of 95 progressives, 90 moderates and 24 “Blue Dog” conservative Democrats. Die-hard Dem voters are certainly moving leftward, but the quality candidates who win in competitive seats are embodied by first-term Reps. Elissa Slotkin of Michigan, Mikie Sherrill of New Jersey, Chrissy Houlahan of Pennsylvania and Virginians Abigail Spanberger and Elaine Luria.

They are women with military and intelligence experience who avoid twitter fights or obsessing over impeachment proceedings against President Trump. They are serious lawmakers who are taken seriously by both sides of the aisle on Capitol Hill.

While the Democratic presidential frontrunner, former vice president Joe Biden, is a moderate who enjoys the “most electable” tag, even this old-school pol has to fight off GOP criticism that uses the socialism label like a spear. lThat albatross was foisted onto the party by Sanders, Warren and some of the outspoken left-wingers in Congress.

If the “resistance” does not believe that their views could drag down the party in 2020, consider what happened last week in a special election for the House in North Carolina. The Dem candidate, Dan McCready, lost by just two percentage points in a congressional district that Trump carried by 12 points in 2016. Party activists viewed that outcome as a moral victory.

But the Dems should pay heed to the way the Republicans ran that campaign. McCready is a Marine veteran. He doesn’t support Nancy Pelosi as speaker of the House. He opposes Medicare for all and an assault weapons ban.

But his Republican opponent and the GOP strategists ignored his background and his views and created a cardboard cut-out candidate that sounded more like Rep. Alexandria Ocasio-Cortez than Dan McCready.

They said McCready is part of the “radical left,” and he’s “right in line with the ultraleft.” In Trump-like fashion, they gave him a sing-song nickname, “Greedy McCready.”

They said his election foe, Dan Bishop, represents “a choice between freedom and opportunity vs. socialism.” And, at an Election Eve rally, Vice President Mike Pence told the crowd that McCready embraces “the far-left agenda” of Pelosi.

The strategy is abundantly obvious. Truth be damned. Anything outside of the GOP narrative is fake news.

So, if the Democrats cling to their left flank, they will be handing to Trump all the ammunition needed to wound the opposition and secure another four years in 2020.