WASHINGTON >> One of the largest outside Democratic groups says ramped-up spending on digital advertising played a key role in midterm battleground races, offering a lesson for potential presidential contenders in 2020.

“You’re going to have to have an organization that speaks directly to voters on their phones and their computers,” said Guy Cecil, chairman of Priorities USA, which spearheaded much of the party’s digital effort during the recent midterm elections. “If the presidential candidates do not have that as a central part of their operation, they will not win.”

Democrats are trying to draw in new voters who are young, diverse and college educated. But at a time when cord-cutting millennials and their parents alike are spending more time online, the party remains disproportionately committed to TV advertising, strategists say, a dynamic that could complicate those efforts.

“Who is watching broadcast television, who is watching Wheel of Fortune, who is watching Jeopardy? They are older, white and they tend to not be Democratic voters,” said Tim Lim, who worked on the campaigns of former President Barack Obama and Hillary Clinton and is now a fellow at Georgetown’s Institute of Politics. “By focusing so much on broadcast TV ads, we are missing crucial audiences to talk to.”

But it’s not just about how much is spent online; it’s about how that money is spent.

While Democrats have been wildly successful at using online advertising to rake in millions in donations and build email contact lists from their base, they’ve lagged behind Republicans when it comes to winning over new or on-the-fence voters in the digital space, operatives in both parties say.

A spokeswoman for the Democratic National Committee did not respond to a request for comment. However, there are signs that the party is making improvements.

One bright spot for Democrats was Priorities’ $6.3-million digital effort that supported Senator-elect Kyrsten Sinema’s win over GOP Rep. Martha McSally in Arizona, a red state that has shown signs of trending toward Democrats.

The goal was driving up overall turnout, with an additional focus on several key demographic groups, including Latinos and whites without a college degree. One set of slickly produced “social pressure” and motivational ads featured a diverse group of actors making the argument for why voting matters.

At the same time, a separate prong of the campaign was aimed at reducing support for a Green Party candidate who later dropped out and endorsed Sinema — a late-breaking development that was highlighted in online ads.

As evidence the campaign helped, Priorities noted in a memo provided to The Associated Press that turnout was up overall and Sinema performed better than Democrats in the recent past with the groups that were targeted.

“We have definitely closed the gap from the previous cycle, but it doesn’t mean we’re entirely there yet,” said Cecil, whose group spent roughly $50 million overall on digital advertising during the midterms.

Though Democrats are behind when it comes to online advertising, an aversion to big spending on digital is not entirely unique to them when compared to the corporate world. While hard numbers are difficult to come by, both parties tend to spend vastly less than is common among corporate advertising clients, where digital spending averages around 40 percent — more than what is normally spent on TV.

It’s also hard to tell how the parties are spending their online advertising dollars because much of the publicly available data does not differentiate between ads geared toward fundraising and email list building versus ads aimed at winning over voters.

Still, there are some broader trends that can be looked at.

After being outspent by Republicans on Facebook in 2016, Democratic campaigns and aligned outside groups had outspent Republicans by more than a 2-to-1 margin on the platform as of last month, according to Facebook data compiled by Democratic digital advertising firm Bully Pulpit International.

“Facebook is the best platform for lead generation and digital fundraising, which explains why Democrats are using it to channel the outrage of their base into email addresses and donations,” said Michael Duncan, a partner and digital strategist at the Republican firm Cavalry LLC. “But when it comes to persuasion (of undecided voters), video overall — and Google specifically — are better platforms.”

That’s where Republicans have outspent Democrats.

A late onslaught of digital spending by a slew of outside progressive groups during the closing weeks of the midterms narrowed Republicans’ spending advantage on Google from 1.65-to-1 down to 1.18, according to data compiled by Bully Pulpit.

But Democrat’s online spending figures are also skewed by the candidacy of Beto O’Rourke, a West Texas congressman who unsuccessfully challenged Sen. Ted Cruz. O’Rourke shattered records, raising more than $70 million. He spent more than $8 million on Facebook ads and $1.8 million on Google, according to disclosures by both companies.

Republicans say they used to be where Democrats are now. Then, after the GOP lost the 2012 presidential race, the Republican National Committee mandated that the party devote serious resources to digital advertising.

Now they sit atop a sophisticated, data-driven digital enterprise that is updated in real time and can micro-target voters based on specific issues.

“We’re getting to the point where digital has the scale of television with the targeting of direct mail,” said Duncan, the Republican strategist. “There are all sorts of ways you can slice and dice a voter file, match it to profiles online and serve ads.”