After a slow start, President-elect Donald Trump appears to be making a concerted effort to place women in his Cabinet. That's great for the women he chooses. It's not so great for those they leave behind: Each time he chooses a GOP female elected official, he'll be reducing the GOP's already slim ranks of female elected officials.

Perhaps the best illustration of this is Rep. Cathy McMorris Rodgers (R-Wash.), widely expected to be named Trump's pick for interior secretary in the coming days. If confirmed by the Senate, she'd be only the third female interior secretary in U.S. history. But Trump would also be taking House Republicans' top-ranking woman out of the chamber entirely. In fact, he'd be taking their only female leader in 2017. (By comparison, Democrats just elected two women to leadership positions.)

The departure of McMorris Rodgers from Congress would underscore a challenge her party has struggled with for decades: its difficulty elevating women to leadership roles. If you're a woman in Congress — and only 20 percent of Congress is female, despite women making up 50 percent of the population — there's a 3 to 1 chance you're a Democrat. Democrats have simply been investing in recruiting women longer than Republicans have, and women voters tend to lean more Democratic than Republican.

For most of the 2000s, the ranks of Republican women in Congress have been stagnant, at about 10 percent of the GOP caucus. (They'll start 2017 with 21 GOP House lawmakers, which is par for the course.) When my colleague Elise Viebeck asked where all the high-ranking GOP women are, she found Republicans had added a net of only two new female lawmakers and virtually no women in leadership (besides McMorris Rodgers, in her role as chair of the House Republican Conference) in more than a decade.

So it stands to reason that Republicans will want to replace McMorris Rodgers with a woman. But who? Underscoring their gender parity problem, there's no obvious choice. What would traditionally be considered her most likely successor — the incoming vice chair for 2017 — is a man.

At least four women are thinking about running for the vacancy:

  • Rep. Mimi Walters (R-Calif.): Elected in 2014 to an Orange County area district, her GOP class also elected her as their representative to the House Republican Conference that McMorris Rodgers chairs.
  • Rep. Susan Brooks (R-Ind.): Elected in 2012 to represent the suburbs of Indianapolis, Brooks briefly ran for governor when Trump chose then-Indiana Gov. Mike Pence to be his vice president, and she'll start 2017 as chair of the House Ethics Committee.
  • Rep. Mia Love (R-Utah): Elected to a swing district in 2014, Love is the first black Republican woman to be elected to Congress.
  • Rep. Lynn Jenkins (R-Kan.): After being elected to Congress in 2008, Jenkins was elected vice chair of the House Republican Conference in 2012. She had planned to step down from that job next year to consider a run for governor of Kansas in 2018. But now that the slot above her may be open on the Hill, she is considering a run for McMorris Rodgers's job.

Besides Jenkins, all three of these women are relatively new to the Hill, which brings me to my next point: When women run for office, they win at the same rate as men, said Debbie Walsh of the Center for American Women and Politics at Rutgers University. There just aren't enough women running, especially Republican women. Of the 10 viable Senate candidates in 2016, just three were Republican.

Some Republican female leaders think Trump didn't do them any favors in terms of recruiting women to replace ones he's taking from them.

But of course, it isn't all on Trump: Well before his election, Republicans were struggling with gender diversity at all levels of government.

While Democrats elected three new women of color to the Senate in November, bringing their total to 16, Republicans lost one of their women, knocking down their total from six to five.

And as Trump tapped Gov. Nikki Haley of South Carolina to be his United Nations ambassador, GOP female governors' ranks slimmed from three to two.

(Actually, both parties severely lack female governors. Democrats have two right now. And GOP female governors could rise back up to three if Iowa Gov. Terry Branstad (R) is confirmed to be Trump's ambassador to China. He'd be replaced by Lt. Gov. Kim Reynolds (R), who could become the first female governor of Iowa.)

If Republican women simply have a pipeline problem, there are efforts at the state level — led by the Republican State Leadership Committee — to recruit, train and support more GOP leaders.

But pipelines take a while to fill, and thanks to a new Republican administration, Republicans are losing female leaders faster than they can replace them.