By: Molly Beck of the Milwaukee Journal Sentinel

MADISON - A number of familiar names — and two newcomers — are swirling in the wake of U.S. Rep. Jim Sensenbrenner's stunning announcement he won't seek another term after more than four decades in Washington.

The departure of "the dean" of the Wisconsin congressional delegation has opened a floodgate of potential Republican candidates in the 5th Congressional District, Wisconsin's most conservative district.

Sensenbrenner's advice to them?

"Don't kill each other, please."

Among the potential Republican contenders are Senate Majority Leader Scott Fitzgerald, Waukesha County Executive Paul Farrow, former Republican U.S. Senate candidates Kevin Nicholson and Leah Vukmir, state Sen. Chris Kapenga, and state Rep. Adam Neylon.

Matt Walker, son of former Republican Gov. Scott Walker, and Ben Voelkel, a Waukesha native who works for U.S. Sen. Ron Johnson, are also considering running for the seat. 

"It's going to be the charge of the right brigade," said Brandon Scholz, a former executive director of the state Republican Party.

"It's such a valuable seat and it doesn't come open very often," said Brett Healy, president of the conservative MacIver Institute. "And then once you're in, you're in one of the most secure Republican seats in the country. I think everyone's going to kick the tires."

Sensenbrenner, 76, said Wednesday evening he won't run for a 22nd term in 2020 — catching off guard some Republicans living in his district who have been waiting for years to hear those words but had stopped expecting to hear them anytime soon. 

Fitzgerald, the leader of the state Senate from Juneau, suggested Thursday his work with former Gov. Scott Walker to pass landmark legislation in 2011 to eliminate collective bargaining for most public employees gives him an edge in the wide field.

"Everybody knows that D.C. is a mess, and in need of more Wisconsin-style common sense," Fitzgerald said. "President Trump needs strong allies to fix it and in the coming days I’ll be seriously weighing a run for Congress with my family and my team."

Farrow told the Milwaukee Journal Sentinel he was shocked by the news of Sensenbrenner's retirement and would be talking over the possibility of running with his family in the coming days. 

Vukmir, who served in the state Senate as assistant majority leader to Fitzgerald, said Thursday she is "strongly considering this terrific opportunity."

"Congressman Sensenbrenner has enormous shoes to fill, he’ll be missed," she said. "I look forward to making a decision in the coming days.”

Vukmir challenged Democratic U.S. Sen. Tammy Baldwin unsuccessfully in 2018 after defeating Nicholson, a businessman from Delafield. 

Nicholson also could run. On Wednesday, he wrote on Twitter: "There will be time to make a decision about this race later."

Neylon, a former Sensenbrenner staffer from Pewaukee who was elected to the Assembly in 2013, said he's considering a run but hasn't made a decision yet. Kapenga told the Associated Press he's "definitely" looking at a run.

Voelkel, who works for Johnson and has done campaign work for Johnson, Scott Walker and Tommy Thompson, and Walker are also considering running for what would be their first effort to seek public office. 

One area Republican who likely won't be running for Sensenbrenner's seat: former Lt. Gov. Rebecca Kleefisch. Her allies are focused on laying the groundwork for her to run for governor in 2022, according to a source close to Kleefisch.

Democrat Tom Palzewicz, who challenged Sensenbrenner in 2018, also said Wednesday he will run for the seat in 2020. Last time, Sensenbrenner beat Palzewicz 62% to 38%.