Stack has represented the 5th District, which covers most of Northeast Philly, for 13 years.
Critz, a longtime staffer to the late U.S. Rep. John Murtha, won that seat after Murtha's death and was ousted after one term.
They don't seem to have much in common, except the instinct to point out the other guy's faults.
Critz said he was "distressed" by a question Stack asked his primary foes Wednesday in a joint appearance on WITF, a public radio station in Harrisburg.
Stack asked, "If they strongly disagreed with what the governor was doing, would they stand up and be counted?"
Critz said he would be a "team player" and asked Stack if he would "publicly oppose" the governor as lieutenant governor.
Stack replied: "If I strongly disagreed, absolutely."
Stack yesterday knocked Critz for votes in Congress that have prompted a coalition of liberal groups active in abortion rights, the environment and LGBT issues to send out anti-Critz mailers in western Pennsylvania.
"I think he's out of touch with Democratic values and progressive ideas," Stack said.
Critz called that nothing new.
"It's something I faced as a congressman," he said. "Being a moderate, I get hit by both sides."
Harrisburg City Councilman Brad Koplinski, Bradford County Commissioner Mark Smith and state Rep. Brandon Neuman of Washington County round out the field and are polling in the single digits so far.
A Stack-Critz matchup reminds us that Pennsylvania is a big state and geography is a factor for statewide races.
Critz emphasizes his strength in western Pennsylvania as an asset useful to the Democratic nominee for governor. While Wolf is from York, his competitors - U.S. Rep. Allyson Schwartz, state Treasurer Rob McCord and former state Environmental Secretary Katie McGinty - all hail from the state's southeast.
All that political activity in this corner of the state, and a hotly contested 13th District U.S. House seat in Northeast Philly and Montgomery County, will boost voter turnout here. That sounds like good news for Stack.
We could almost hear Stack smiling broadly on the telephone when we brought that up.
"Timing is everything," he said.
So a robot calls and . . .
In this age of Web videos and Twitter feuds, the Democratic race for the 13th District U.S. House seat has gone back to the good old-fashioned robocall.
Former U.S. Rep. Marjorie Margolies has Montgomery County Democratic Committee Vice Chairwoman Joanne Olszewski on one robocall compare state Rep. Brendan Boyle to "tea-party Republicans like Ted Cruz and Rand Paul" because Boyle voted for legislation increasing regulation of abortion clinics.
Half of the 13th District is in Northeast Philly, the other half in Montgomery County.
In another call, Olszewski says the seat should be held by a Montgomery County resident, declaring: "If we lose this district to someone from the city, it will be gone for a long time and it will change the face of politics in this county."
Boyle counters with a trio of robocalls, defending his position on "women's health issues" and accusing Margolies of using desperate "smear" tactics.
"On May 20, tell Marjorie Margolies to take her dirty smear campaign and sleazy politics back to where she came from," former Philadelphia Sheriff Barbara Deeley says in one of them.
" He's gotten a pass on everything. And I really think Sarah Palin has exactly the right message for women, because we know in our lives we don't get a pass."
- Lynn Forester de Rothschild, slamming then-U.S. Sen. Barack Obama and praising then-Alaska Gov. Sarah Palin on Fox News during the 2008 presidential election.
She hosted a fundraiser for Margolies yesterday evening at her Manhattan home with former U.S. Secretary of State Hillary Clinton. Margolies did not attend. Her son, Marc Mezvinsky, is married to Clinton's daughter, Chelsea Clinton.