A pair of vulnerable Republican senators are targeting their Democratic opponents over national security in the wake of the Brussels terrorist attacks. 

Sen. Ron Johnson (R-Wis.), asked about the importance of security in the upcoming election, quickly pivoted to former Democratic Sen. Russ Feingold’s vote against the Patriot Act in 2001. 

{mosads}”My opponent, Sen. Feingold, was the only senator that voted against giving our national security and law enforcement individuals the tools they needed to keep this nation safe,” he told a local radio station Wednesday. “Voters need to keep that in mind: who is actually for national security, and who is going to be dangerously weak on it.” 

Feingold cited concerns over First Amendment violations and undermining due process during a floor speech explaining his vote against the Patriot Act.

Republicans have repeatedly targeted Feingold on national security and foreign policy. They’ve been eager to tie the former senator to the Obama administration, particularly on his support for the Iran nuclear deal. 

Johnson has also touted his role as chairman of the Homeland Security and Governmental Affairs Committee, where he oversees the Department of Homeland Security. 

His comments come after the Tuesday attacks in Brussels, which killed at least 31 people and sparked concern from GOP lawmakers who say Obama isn’t doing enough to defeat the Islamic State in Iraq and Syria (ISIS).

Sen. Mark Kirk (R-Ill.) tweeted after the attacks that “it’s even important to note the [national] security contrasts” between himself and Rep. Tammy Duckworth (D-Ill.). 

A Kirk campaign memo released last week touts his positions on national security, including his opposition to closing Guantánamo Bay and support for cracking down on accepting refugees.

“Sen. Kirk is providing national leadership on security issues at a time when Iran is saber rattling and expanding their influence across the Middle East and ISIS is printing fake passports and infiltrating the West to conduct horrific acts of terror,” the memo says.

Kirk was among a handful of Republicans who quickly called for the administration and Congress to re-examine the refugee acceptance program following Tuesday’s attacks.

Wednesday’s comments are the latest example of Republicans focusing on national security as they look for an edge in their battle to keep the Senate in November. Republicans are defending 24 Senate seats but can only afford to lose a handful.

According to an NBC/Wall Street Journal poll released late last year, only 34 percent of Americans approve of the president’s handling of ISIS.

Republicans, however, aren’t alone in focusing on their national security credentials in the wake of Tuesday’s attacks.

Former Rep. Joe Sestak, a Democrat who is competing to take on Republican Sen. Pat Toomey, sent out a memo Wednesday outlining five principles of how to defeat ISIS.

“Yes, I’m running for the U.S. Senate, but I’m fairly unique not only amongst those across our nation running for public office at almost any level, but also of anyone down there in the Senate in either side with the breadth and the depth of experience,” he told reporters during a conference call.

Sestak, who was a member of the Navy and the White House National Security Council, added it was “incumbent” on him to talk about the “proper strategies,” saying there is “an absence of leadership in my party, and definitely in the other party.”

Ted Kwong, a spokesman for Toomey’s Senate campaign, fired back at Sestak Wednesday. 

“It was just last year Joe Sestak adamantly defended the Obama administration’s failed approach, saying ISIS was ‘almost out of gas.’ Sestak’s extreme liberal policies are not the ‘proper strategy’ to fight radical Islamist terrorism,” he said.  

– Updated at 6:37 p.m.