DES MOINES, Iowa (AP) — Democrats and Republicans once largely agreed that the upcoming midterm elections would hinge on the economy, health care and President Donald Trump's popularity. Not anymore.

A Supreme Court vacancy has pushed abortion to the forefront of election year politics, with both supporters and opponents suggesting that the emotional issue could drive more voters to the polls. That's especially true in states like Iowa, where Republicans have enacted restrictive measures on abortion in the past two years.

"It could very well drive energy and enthusiasm nationally," said Paul Harstad, a veteran Democratic pollster who for decades advised former Iowa Sen. Tom Harkin. "But Iowa is a case where it's getting to be on the front burner. The issue has become very real in Iowa."

__

EDITOR'S NOTE: Associated Press reporters are on the ground around the country, covering political issues, people and races from places they live. The Ground Game series highlights that reporting, looking at politics from the ground up. Each week, in stories and a new podcast, AP reporters examine the political trends that will drive the national conversation tomorrow.

__

WHAT'S HAPPENING

A pair of recent abortion restrictions in Iowa have made the state a focal point in the national debate.

A late-June decision by the Iowa Supreme Court to strike down a required 72-hour waiting period before an abortion sparked outrage among Christian conservatives, a potent force in the Iowa GOP. It also emboldened Democratic nominee for governor, Fred Hubbell, who is a past Iowa leader of Planned Parenthood, and underscored the contrast with Republican Gov. Kim Reynolds, who opposes abortion in all cases except to save a mother's life.

The decision, which asserted "autonomy and dominion over one's body go to the very heart of what it means to be free," also bodes ill for the even more restrictive law Reynolds signed in May but was blocked pending court review.

That law, the nation's most restrictive, banned abortion after the detection of a heartbeat — usually at around six weeks of pregnancy.

"Americans know that when a baby's heart is beating, she's alive, but our state judges aren't willing to protect her life," Chuck Hurley, a vocal opponent of abortion rights in Iowa, proclaimed from the Iowa Capitol steps in Des Moines.

WHY IT MATTERS

In Iowa, abortion rights have motivated swing voters in close statewide races. Polls have shown that the issue can motivate votes for Democrats who have characterized a Republican opponent as extreme.

That said, an uptick in turnout among Christian conservatives allowed President George W. Bush to narrowly carry Iowa in 2004, aided by late-campaign radio ads noting the Republican's opposition to abortion rights and same-sex marriage.

This year, the Supreme Court vacancy comes as Democratic-leaning voters are already motivated, as seen in voter registration, turnout and primary victories by liberal Democrats.

"You might have had a history of the other side using the courts as an issue," said Ilyse Hogue, president of NARAL Pro-Choice America, a leading national abortion rights advocacy group. "What I think you heard from all our organizations is that people who are voting in these states are fired up."

And Iowa is not alone as a key midterm battleground with recent abortion rights developments at least in the background.

In Republican-leaning Indiana, a federal appeals court struck down in April a law signed in 2016 by Republican then-Gov. Mike Pence banning abortions based on a fetus's gender, race or disability. The issue creates a difficult dance ahead for that state's Democratic Sen. Joe Donnelly, a moderate on abortion rights seeking re-election in a state Trump carried by 19 percentage points in 2016.

WHAT TO WATCH

Advocacy groups on either side of the abortion rights debate are heaping pressure on candidates viewed as key to the balance of power in the Senate.

Susan B. Anthony List, a group that opposes abortion rights, has dispatched more than 500 local workers not just in Indiana, but Florida, Missouri and Ohio, where Democrats are also seeking re-election in states Trump carried in 2016. After Supreme Court Justice Anthony Kennedy announced his retirement, the group said it is adding North Dakota and West Virginia.

Democratic Sens. Heidi Heitkamp of North Dakota and Joe Donnelly of Indiana are both seen as key votes on Kennedy's successor.

"The enthusiasm on the other side is something to be aware of, but we have every reason to be encouraged," said Mallory Quigley of Susan B. Anthony List. "The left is incensed. But it also buoys the base on the right that is encouraged that we have a president following through on a pro-life agenda."

Conversely, in Nevada, Democratic Senate challenger Jacky Rosen is accusing Republican Sen. Dean Heller, who opposes abortion rights, of being out of step with voters.

Heller is the only Republican seeking re-election in a state Democrat Hillary Clinton carried in 2016. Also, Nevada's popular, departing Republican Gov. Brian Sandoval supports abortion rights, which were enshrined in the state's constitution almost 30 years ago.

"We're going to hold Sen. Heller's feet to the fire," Rosen said in an Associated Press interview. "Nevada is a pro-choice state."

DON'T MISS

Democratic senators have urged Trump and Senate Republicans to wait until after the midterm elections to move ahead with Kennedy's successor, though the Republicans have shown no appetite for delaying the confirmation process.

Minority Leader Chuck Schumer of New York called the GOP's tack "the height of hypocrisy," in light of the GOP-controlled Senate's refusal to consider then-President Barack Obama's nominee before the presidential election in 2016 after the death of Justice Antonin Scalia.

But confirmation of a Trump nominee before the election could mollify those devout conservatives who might have been motivated to vote if a court pick were on the line, said Harstad, the Democratic pollster who also advised Obama's campaigns in 2008 and 2012.

"It's not a certainty. But I think, once a justice is confirmed, the evangelicals will feel safer and it may actually inhibit their turnout," Harstad said.