Two minutes after San Antonio Mayor Julián Castro arrived at Tom Harkin’s annual Steak Fry in Indianola, Iowa, he was holding a spatula behind a grill, posing with it in between Harkin, the state’s Democratic senator, and Vice President Joe Biden.

“These are Iowa steaks,” Harkin told him, “and they’re a lot more tender than that Texas stuff.”

It was all in good fun, though; Harkin later led the crowd in singing “Happy Birthday” to Castro and his twin brother, Joaquin, who was elected to Congress last year. And so Mayor Castro refrained from bragging about his state’s reputation for some of the best meat in the country the world. There would be other opportunities during his keynote speech to brag about more important things happening in Texas, and in San Antonio.

Bragging, that is, or campaigning. The steak fry is a fundraiser for Harkin’s PAC. It has been held every year since 1979, when Harkin was elected to the U.S. House of Representatives (he was eventually elected to the Senate in 1985). Over that time, Harkin’s fundraiser has drawn plenty of big-name Democrats, like Biden, who made a few jokes about what his own plans might be in 2016. In 2007, every official candidate for the Democratic presidential nomination smiled with their spatulas and steaks the same way Castro and Biden did this year. And the steak fry is also a spot for up-and-comers. Bill Clinton spoke here before he became president, as did Obama—in 2007, when he was officially running for the 2008 nomination, but also in 2006, when he was still a little-known senator from Illinois.

In other words, the fry may be considered, as the Des Moines Register puts it, “a stepping stone to the White House.” Castro, who was elected to his final two-year term as mayor earlier this year (term limits), has repeatedly said that he’s focused on San Antonio for now, politely deflecting speculation in Texas about whether he might run for statewide office in 2014, or for national office at some point beyond that. That didn’t stop many Iowans from speculating anyway, though.

“I was surprised to see him on the list. I wondered if he had any national aspirations,” said Miko Wilford. “I don’t know why else he would be here.”

“I think he might put a bid in for president. If you wanna get elected, you better come up to Iowa,” Barbara Cunningham said.

Skip Phillips already thinks it’s bound to happen: “He’ll be one of the best candidates to come out of Texas.”

The Iowans who knew Castro before this weekend, for the most part, had learned of him during the 2012 Democratic National Convention, where he gave the keynote speech (as did Obama in 2004, but who’s keeping track?). Castro’s steak fry speech, like that 2012 keynote, focused on the importance of education. He highlighted the day he and Joaquin received their Stanford University acceptance letters.

“The only reason I was able to reach my American dream and go to college and become a professional was because I worked hard and my family worked hard, but because there were Pell Grants and Perkins Loans and work-study,” said Castro. “In other words, because I invested in myself. But fundamentally, I reached my dream because you invested in me. Because the American people invested in me. That’s what’s great about this nation.”

It was an applause-generating high point of his spiel, and Castro went on to discuss San Antonio’s new universal pre-K initiative, which voters approved in 2012. The program only took effect this January, so it’s too early to tell what its results will be, but observers have high hopes; most education experts agree that pre-k education is a critical intervention for children, and extending access to pre-K has been a goal for both Democrats and Republicans around the country. “I have been trying for 20 years to get something done for early childhood education,” Harkin said in his own speech. “The mayor of San Antonio decided not to wait.”

Castro and his brother’s embodiment of the American dream served as a useful reference point for Democrats like Biden and Harkin. Both of them, in their own speeches, spoke on the importance of serving the middle class and giving everyone an equal chance at opportunity. America increasingly looks more like Texas than Iowa, though, and so it meant something to have a young, Hispanic, Texan politician—Castro is only a few years older than the steak fry—at the table with the mostly older, mostly Anglo Democrats of Iowa.

“My family story is like theirs: it’s an American dream story, and we need to continue to invest in opportunity for America to prosper in the 21st century,” Castro said to me later, on the walk to the car. “So hopefully they recognized that.”

Castro once again demurred about his future plans. “[Harkin] asked that I would come up here and support Bruce Braley as he runs for Senate,” Castro continued, referring to a Democratic congressman who is running to replace Harkin, who is retiring. “Joaquin and I have both travelled to different states helping Democrats get elected. Since I’m not on the ballot, I’m able to do that.” Joaquin Castro, who was traveling with his brother, agreed: they were mostly “energizing Democratic voters.” The two have been on a multi-state tour, and plan to hit 11 states by the end of October.

Texan Democrats might well grumble that if the Castros want to energize Democratic voters, they could focus on doing so in Texas. For the past few months, since Fort Worth senator Wendy Davis’s daylong filibuster, local liberals have been cautiously optimistic about the party’s prospects, but only cautiously. Among the pitfalls is the fact that (other than Davis, who is planning to announce her plans shortly) none of the state’s most high-profile Democrats, including Julian Castro, is planning to run for top office in 2014.

But if Castro does run for something else in 2014, or 2016, or 2018, he will, at least, have laid some groundwork.

“[His speech] was incredible,” another Iowan, Randy Black, said afterward. “He gave me the same feeling when I heard Barack Obama speak for the first time in 2004. I knew when I heard Barack speak he was going somewhere. This man, Castro, is going somewhere.”

Even if it’s not to D.C.