For all the attention on battleground polls giving Hillary Clinton the edge, Donald Trump enjoys at least one electoral advantage in his uphill climb to the White House: Republicans are outpacing Democrats in registering new voters in key states.

A review of registration figures shows that in the swing states that sign up voters by party, Republicans are seeing a significantly bigger boost since 2012. In states like Florida and Pennsylvania, the party has added tens of thousands of voters to the rolls at a time when Democrats have seen their base shrink.  

“The numbers [in those states] … are a huge shift from what we’ve seen in 2012,” Republican National Committee spokeswoman Lindsay Walters said.

The surge doesn’t change the fact that Clinton leads, if only by a thin margin, in most battleground state polls, which presumably reflect the current voter make-up.

Fox News ratings show Clinton maintains the advantage in the Electoral College, while a Washington Post survey this week of registered voters in all 50 states reflects a similar dynamic. And in big swing states ranging from Florida to North Carolina to Pennsylvania, there are still more registered Democrats than Republicans.

But the registration shift since 2012 suggests Trump will enjoy a stronger base of GOP voters in some states than did Mitt Romney four years ago.

In Florida, numbers from the secretary of state show Republicans gained 162,000 voters since 2012; Democrats lost nearly 137,000.

In Pennsylvania, Republicans gained 40,000 voters; Democrats lost 178,000.

And in North Carolina, both parties lost members as the number of unaffiliated voters rose. But Democrats lost far more than Republicans in the last four years.

Not all states register voters by party, but a review of eight states that do – Arizona, Colorado, Florida, Iowa, Nevada, New Hampshire, North Carolina and Pennsylvania – showed Democrats since 2012 signed up more than Republicans only in Arizona and Colorado.

Changes in registration can be driven by a range of factors: Young voters coming of age and registering; voters switching parties, voters moving from state to state; and adults registering for the first time.

An RNC official involved in registration efforts told FoxNews.com the bulk of the changes reflect new sign-ups. The official said the party has been putting more emphasis on registration “than at any time since 2004.”

Staffers are going to fairs, churches and door-to-door – and especially Trump/Pence rallies with that goal in mind.

“We’re walking away with a ton of new registrants from those [rallies],” the official said. According to the party, staff and volunteers to date have knocked on millions of doors and registered nearly 725,000 new voters.

The RNC, though, expects Democrats to step up their own registration efforts over the course of the next month as deadlines approach. 

For its part, the Clinton campaign launched a major registration effort at the start of the Republican National Convention in July, setting a goal of signing up more than 3 million.

“Since the Democratic National Convention, more than 600,000 phone bank, canvass, or voter registration shifts have been completed,” a Clinton campaign official told FoxNews.com.

The official said the nominee and running mate Tim Kaine, along with other surrogates, will continue hosting voter registration events across the country. Most recently, Clinton held one Thursday in Charlotte, N.C. The campaign is planning to use upcoming events with President Obama and first lady Michelle Obama as opportunities to register more in big swing states. And ahead of the state’s Oct. 11 registration deadline, the campaign is launching what it calls a “Campus Day of Action” across Pennsylvania campuses on Saturday to register students.

“Our goal is to make sure every student has their voice heard on Election Day,” Hillary for Pennsylvania Youth Outreach Director Kyron Banks said in a statement. 

The RNC also is planning a “National Day of Action” Saturday during which thousands of staff and volunteers will knock on doors in battlegrounds, with registration a major focus. 

Fox News’ Steve Carlson contributed to this report.