WASHINGTON — Sen. Alex Padilla (D-Calif.) has joined the bipartisan effort to prevent another Jan. 6, 2021-style attack on the U.S. Capitol, signing on this week as a co-sponsor of legislation that would update a 135-year-old law known as the Electoral Count Act.

The Senate proposal, introduced in July, already had the backing of 10 Republican senators, ensuring it can pass the chamber so long as all Democrats and the two independents who caucus with the party support it. But senators signaled earlier this month that the bill, which would reform the certification process for electoral votes, is unlikely to get a floor vote until after election day.

The House unveiled competing legislation this week.

The lower chamber approved that bill on Wednesday by a vote of 229-203, with nine Republicans joining all but one Democrat, who didn’t vote, in support of the measure.

Padilla spoke to The Times shortly before the House vote on Wednesday. Below are excerpts from the conversation, edited for clarity and length.

What was the process like for you getting on board with this legislation?

I’ve been talking about elections and the big question of how do we make sure the insurrection that we saw last Jan. 6 doesn’t happen again. [There were] a lot of factors that went into how the day played out, but one of the biggest is if you consider an ambiguity in the law that was exploited by the insurrectionists to disrupt the peaceful transfer of power and try to undo what was a free and fair election.

So shoring up that language is part of ensuring that an insurrection like we saw on Jan. 6 doesn’t happen again. We’ve had broader reform, voting rights, access to the ballot debates and conversations in committee, even on the Senate floor last year, but in recent months there was a lot of momentum building on updating the Electoral Count Act specifically.

I think it’s an important step that we should take before the end of the year and then continue to work on the other pieces.

Was the process like just a lot of conversations, meeting with members and getting a feel for what they were trying to do?

It’s bipartisan. I wanted to make sure that it wasn’t a complete like, “We’re just going to do this and forget about voting rights and access to the ballot concerns that exist in a lot of states,” but the more I had conversations with my colleagues, I know that there was real support behind something like this.

I’ve seen this proposal described, as you said, as a way to prevent another Jan. 6. Is this how members should speak to constituents about the bill?

I think it’s a key part. Absolutely. There’s a lot of laws on the books that haven’t been touched in a while that were written in a different era, and so much in our society has changed. So if by adding the clarifications [we help] ensure the peaceful transfer of power after future elections, then it’s absolutely critical.

Is there any concern that changing the language will backfire with people who do believe that there was widespread voter fraud and that the election was stolen?

Look, one thing you can’t control is what comes out of [former President] Trump’s mouth, so I can’t worry about that.

The way Trump has been effective in whipping up his supporters is making it very, very partisan, and so the fact that this has significant bipartisan support, I think, is a strong signal for the public.

[Senate] Democrats were all presumed to support this legislation because it has enough Republican support to pass the Senate. Was your support ever truly in doubt?

First of all, details matter. And there’s a lot of sort of substantive pieces that have been discussed, kind of ironed out. You’ll see some technical amendments when the Rules Committee convenes on Tuesday, and maybe there are ways to further strengthen the bill.

Is this all we’re going to do from a strengthening democracy front? The answer is no. There’s still important work to be done on ensuring the fundamental right to vote and access to the ballot, similar to what we tried to do with the John Lewis Voting Rights Act, the Freedom to Vote Act and other efforts.

Do you think there are any of your Democratic colleagues in the Senate who are at risk of opposing this legislation for any other reason?

I don’t know. I’m now actively engaged in all those conversations.

I’ve been in touch with a lot of members throughout the day today.

How did your role as a former secretary of state shape your approach to reforming the Electoral Count Act?

As California’s secretary of state, I oversaw the administration of two presidential elections — two primaries and two general elections.

We’re very familiar intimately with every stage of that process, but again, what happened on Jan. 6, the reason people were invited and incited and turned on to Congress was a misbelief that there was the ambiguity in the law, that it could be challenged, that the vice president had authority that he really did not have.

And it wasn’t just a protest. It wasn’t just a rally. It wasn’t just an expression of speech. It turned violent. It turned deadly. And we need to do what’s necessary to prevent an insurrection like that from happening again.

Now that you’re on board with this legislation, is your role at all to convince more progressives to join the effort?

I’m reaching out and fielding calls from a lot of my colleagues on what my thought process was and why I think it’s important, why they should support it. Happily answering those questions and adding to that the urgency.

I think it is important to get it done before the end of the year. If this slips into 2023, who knows how quickly after the November election candidates for president may start announcing, and once there’s official candidates, to talk about changing the rules — even though this is strengthening the rules of how the whole presidential election process plays out — let’s not risk any questions or concerns about it.

Let’s get this done in a thoughtful, clear way and do it well in advance of 2024.

Is there any concern that some Republicans may pull out after the election and decide they don’t want to do this?

I guess that’s always possible. After the last 20 months of being here, nothing should surprise me anymore. But I don’t think so. Certainly not those that have already taken the step of lending their name to the bill. I don’t see that changing after November.

That’s not to say all 50 Republicans will vote for it if and when it’s brought up for a vote.

For those who don’t, I really wonder what their motivations are, what their sincerity is, in terms of commitment to our democracy.