Even with a lot of talk, and even controversy, surrounding HUD Secretary Julián Castro’s possible nomination to become Hillary Clinton’s vice president, there was a lot more going on behind the scenes, preventing him from locking in the bid, according to an article The Washington Post.

In an interview with The Washington Post’s Dan Balz, Castro said:

“It’s disappointing, of course, but it’s also easy to put into perspective. When I was 30 years old, I lost a very close mayor’s race. At the time I was completely disappointed and crushed. But a few years later I came back and I became mayor of San Antonio and it actually worked out for the better.”

In October 2015, Castro was first rumored to not only be on the shortlist as a potential nominee for vice president under Clinton, but perhaps even at the top of that list.

However since then, Castro not one, but twice, was called into question for his right to assume the role.

First, in April 2016, according to a report from Politico, a cadre of progressive groups targeted Castro in an attempt to disqualify him as Clinton’s nominee, using HUD’s practice of selling non-performing loans to private investors as their weapon.

Then in July, right before Hillary announced her VP pick, Castro was cast into the limelight for discussing soon-to-be Democratic presidential nominee Hillary Clinton during an April interview.

 A report from the U.S. Office of Special Counsel found that Castro violated the Hatch Act, which prohibits federal employees from using their official position to influence an election, because the OSC determined that Castro was operating as HUD Secretary during an interview with Yahoo News and therefore prohibited from discussing politics.

But, according to a report from The Hill, the White House will not discipline Castro for the Hatch Act violation.

Although it wasn’t these hurdles that led to Castro not getting picked as vice president, with the bid instead going to Virginia Sen. Tim Kaine, according to the Washington Post article.

The article explained that two things changed between the time he was first seen as a shortlist choice for vice president and the time Clinton made her selection.

One was the rise of Republican nominee Donald Trump and the effect of his candidacy on the Latino vote. Trump’s harsh words toward Mexicans and his stance on immigration appear to have put the Hispanic vote even further out of reach for the GOP.

The other change was the rise of terrorism and security as prominent issues in the campaign.