Twenty-eighteen has been dubbed a "year of the woman" in politics because another two dozen newcomers — maybe more — are likely to get elected to the House of Representatives.
But the situation is surprisingly different in the Senate, where only one seat that's currently held by a man is for sure going to be taken by a woman.
It’s the open seat in Arizona, which is going to elect the first female senator in the state’s history — either Republican Congresswoman Martha McSally or Democratic Congresswoman Kyrsten Sinema.
Their shared gender and membership in Generation X are where the clear similarities end.
They have very different life stories and their ideologies are pretty different, too — although they're not the sort of political polar opposites you see in so many campaigns.
They’re running to succeed Republican Jeff Flake, who decided not to seek re-election. But both are campaigning more about being worthy heirs to the legacy of John McCain, the legendary Arizona senator who died this summer.
A career officer who was the first woman to fly a fighter jet in combat for the Air Force, McSally is emphasizing their shared biography as military aviators and foreign policy hawk Republicans.
She got elected to Congress as a mainstream conservative four years ago and was a frequent Donald Trump critic in 2016.
But this fall she's running as a diehard loyalist of the president's and has voted the way he wants around 98 percent of the time.
Sinema is emphasizing that she's got McCain’s sort of independence and maverick streak.
She grew up in poverty for a time and started her career as a liberal community activist and anti-Iraq War crusader.
But she's moved steadily to the middle and is now one of the most centrist members on Capitol Hill, voting Trump’s way about 60 percent of the time over the last two years — more often than all but three Democrats.
Immigration is an especially divisive issue in Arizona — and perhaps the hottest issue in the race.
Both candidates pledge to fight for more border security. But McSally has shifted hard to the right. She's dropped her past support for allowing so-called Dreamers to stay in the U.S. forever. And she's a big booster of Trump's border wall.
Sinema favors legalization for people brought into the country illegally as children. And she wants more high tech solutions for slowing border crossings than the wall — which she describes as an 18th-century solution to a 21st-century problem.
Their differences are pretty subtle on health care. While McSally voted for the Republican plan to repeal and replace Obamacare last year, and Sinema voted against it, both have moved toward a middle ground.
Each wants to preserve the popular parts of the Affordable Care Act, like protections for people with pre-existing conditions, while relaxing cheaper medical insurance plans than the law currently allows.
In other ways, the differences are clear: McSally voted for the Trump tax cut. Sinema voted against it.
McSally opposes any new federal gun controls. Sinema favors tighter background checks for people wanting to buy firearms.
McSally opposes abortion rights. Sinema favors abortion rights.
Arizona has a longtime Republican lean and hasn't elected a Democratic senator in 30 years. But its growing populations of Latinos and well-educated suburbanites is making the state more and more politically purple every year.
This is one of the closest Senate contests in the country. And it's one of only a handful of states where a Democrat has a real shot at taking a seat away from the GOP – something that has to happen in at least two places for the Democrats to become the majority party.