Denis McDonough was chief of staff to President Barack Obama from 2013-2017. The views expressed in this commentary belong to the author. View more opinion at CNN.

(CNN) In 2016, our democracy was attacked. The Russian government launched an unprecedented series of cyberattacks to disrupt our electoral process that included targeting the people, institutions and vendors that administer our elections.

As President Obama's chief of staff, I saw several people at the time -- including Congressional Republican leaders -- dispute these facts . President Trump and many of his allies still dispute them today even after several investigations have made Russia's actions plainly clear. And Russian President Vladimir Putin, who also denies Russia's interference, has yet to be held accountable.

We have been warned by special counsel Robert Mueller and former Director of National Intelligence Dan Coats that the people who attacked our democracy in 2016 will be back in 2020. Their tactics will be more sophisticated and ruthless than before. And we have to be ready.

But so far, despite bipartisan and widespread concern among intelligence and cyber experts, we have seen nothing but inaction from President Trump and Senate Republicans, increasing the risk of continued attacks on the integrity of our elections.

That's why I support the DNC's decision to reject a "virtual caucus" plan put forward by the Iowa and Nevada state parties. The goal of the Iowa and Nevada plans -- to make caucuses more inclusive and increase participation -- is laudable and in keeping with our party's intense focus on guaranteeing every eligible voter's access to the ballot. And we should continue to explore options that ensure and expand the most fundamental constitutional right: the right to vote.

However, the "virtual caucus" proposal comes with serious cybersecurity risks. Security experts agree that the technology, as it exists now, is too vulnerable and could easily fall victim to hacking by outside actors, including foreign adversaries such as Russia. Given the scale and imminence of the Iowa and Nevada caucuses, Democrats simply cannot take that risk.

I applaud the seriousness with which the DNC is handling this issue. This decision could not have been easy or expedient, but it was necessary. The DNC, which suffered Russian cyberattacks in 2016, is learning from the past and rightly exercising caution by putting the security of our democracy first.

The DNC's prudence stands in stark contrast to the Republican Party's recklessness. Despite the warnings of our intelligence community and the recommendations of cybersecurity experts, Senate Majority Leader Mitch McConnell has blocked efforts to pass critical election security legislation.

Securing our elections should not be a partisan issue. As DNC Chair Tom Perez said earlier this year, "This is not about red and blue. It's about red, white and blue."

We cannot ignore the lessons of 2016. The threats to our democracy are real, and the integrity of our elections is paramount. That's why every American should call on our nation's leaders to take action on this issue immediately and ensure that voters' voices are heard at the ballot box.

Get our weekly newsletter Sign up for CNN Opinion's new newsletter. Join us on Twitter and Facebook

Ultimately, we need to elect a president and a Senate that treat the issue of cybersecurity with the seriousness it deserves. Until then, the DNC is making the right decision. And I'm confident that Iowa and Nevada Democrats will still be able to hold successful -- and secure -- caucuses.