Alexandria Ocasio-Cortez hasn’t even been elected to Congress yet, and she’s already in a dispute with congressional leaders.

After Ocasio-Cortez’s surprise primary victory over one of the top-ranking Democrats in the House, Minority Leader Nancy Pelosi (D-Calif.) sought to downplay the ramifications of one establishment politician getting the boot.

“They made a choice in one district,” Pelosi said in a news conference Wednesday. “So let’s not get yourself carried away as an expert on demographics and the rest of that. We have an array of genders, generations, geography and the rest, opinion, in our caucus, and we’re very proud of that.”

On CNN on Wednesday, Ocasio-Cortez responded. She noted that “it’s not just one district” and that many districts have “extremely similar dynamics” to her own.

“I do think that we do need to elect a generation of new people to Congress in both parties,” she said. “This is about diversity, as well. We have to have a diversity of age represented in Congress, too,” she added later.

There are age limits to the House and Senate. Ocasio-Cortez is 28, three years older than the minimum requirement to serve in the House. If she wins in November, which is likely, she would be the youngest woman to ever serve in Congress and the only one currently serving who is younger than 30.

She would be an exception. But she would especially be an exception within her own party.

The distribution of ages and tenures in Congress (both House and Senate) looks like this:

On the surface, the two parties look roughly similar, a smooth curve from young to old. (The two independents, Sens. Angus King (Maine) and Bernie Sanders (Vt.) are in the middle.) Looking at the parties individually, though, the difference between them is sharp.

Let’s start with the Republican caucuses in the House and Senate.

About a quarter are older than 65, which would in another context be considered retirement age. The party’s leaders (the top two Republicans in the House and the Senate plus House Speaker Paul D. Ryan of Wisconsin) have served a bit longer than the average Republican but are about the same age as their peers.

Most Republicans in Congress are baby boomers, born between 1946 and 1964. Some 29 percent are Generation X, using Pew Research Center’s definitions of generational boundaries. About 8 percent were born during or before World War II; four were born after 1980.

Compare that with the Democrats (and those two independents).

More than 4 in 10 Democrats are older than 65. Nearly 16 percent were born before or during World War II; only one, Rep. Tulsi Gabbard (D-Hawaii), was born after 1980. There is generational diversity as Pelosi claimed, though barely including the two most recent generations (millennials and post-millennials).

What’s more, Pelosi and the rest of the party’s leadership are significantly older than the caucus, which itself is several years older on average than the Republicans.

The leadership of the Democratic Party has been serving in Congress, on average, longer than Ocasio-Cortez has been alive.

This isn’t necessarily a bad thing, of course, but it may help explain why Pelosi made the argument she did at the outset. When Democratic leaders joined Congress on average, it was the early 1980s. The party’s leadership came of age during the moderate Bill Clinton era of political triangulation while the party’s base has grown much more liberal over the past two decades. For Democratic leaders who fought hard for particular incremental changes on policy issues, new candidates and activists calling for more sweeping shifts can seem jarring and unrealistic. If the people surrounding congressional leadership share their same demographics and priorities, the upstarts can also seem hopelessly out of touch with what leaders are hearing about from their peers.

Simply bringing in younger members of Congress won’t necessarily mean that the party is better reflecting the will of the base. (The first millennial in Congress was former Illinois representative Aaron Schock, whose career was not exemplary.) But one can’t both claim that it is good to have diversity of race, gender and age because it broadens the range of opinions and also argue that a caucus in which only eight people are younger than 40, and 35 younger than 50, is sufficiently diverse to represent the country.

Ocasio-Cortez has a point.