There was an unwritten rule among Bucks County Republicans during the four-decade reign of late party boss Harry Fawkes: Avoid a competitive primary at all costs.

Times may be changing.

Two Republicans say they are considering a run for the county's soon-to-be-open Eighth District congressional seat in 2016: State Rep. Scott Petri, of Richboro, and Doylestown businessman Tom Manion, who ran and lost against Rep. Patrick Murphy in 2008. More names could emerge this summer as insiders quietly approach or assess other potential candidates.

Mike Mabin, chief executive of the Bensalem-based steel company PennFab, for example, said he was encouraged to run. He declined.

Whoever accepts will join at least two declared Democratic candidates. Shaughnessy Naughton, a 2014 primary candidate, and State Rep. Steve Santarsiero have been raising money for an anticipated primary battle.

The glut of early interest in the district is no surprise, political observers say. The successful candidate is likely to need millions of dollars to win. With four-term incumbent Mike Fitzpatrick retiring to meet his self-imposed term limit, and in a moderate district during a presidential campaign, the prospect for potential office-holders is tantalizing.

"I think people see this as a great opportunity to have a chance at getting into Congress," said Chris Borick, political science professor at Muhlenberg College in Allentown. "So you'll probably draw a pretty good list of individuals."

That has not always been the case in the district. In the eight GOP primaries since 2000, four were contested, but none ended up being close, state records show.

In 2010, Fitzpatrick earned 76 percent of the vote against three other GOP candidates. In 2000, 2002, and 2004, incumbent Jim Greenwood defeated a single challenger each time with at least 67 percent of the vote.

Democrats have had the same number of primaries, but theirs have been more competitive.

Last year, Kevin Strouse squeaked out a win over Naughton by less than three percentage points before losing to Fitzpatrick in November's general election.

Republicans in Bucks have typically viewed contested primaries as counter-productive, said Charles Martin, a county commissioner since 1995. "You're fighting with yourselves (rather) than against the other party," he said.

Fawkes, the old-school political boss, was famous for preferring a one-candidate field.

Still, this cycle could buck the trend.

State Rep. Gene DiGirolamo, a Republican from Bensalem, decided against entering the race a few weeks ago, but said the field could easily expand.

"I would not be surprised to see one or two or more other people come out and say they're interested on the Republican side," he said, declining to offer any names.

Pat Poprik, who chairs the county Republican Party, agreed. Committee members will not begin formally interviewing candidates until January, she said, so there is plenty of time for other interested parties to emerge.

"It's still early," she said.

Petri and Manion say they are only in the "exploratory" phase of a potential campaign, gauging their support before deciding whether to declare a bid. Manion said he hopes to decide by the end of this month.

Randall Miller, a political science professor at St. Joseph's University, said any potential nominee will have to start raising money quickly. The cost of a victory could exceed $5 million, he said.

The race is "going to attract an enormous amount of national attention," he said.