ST. PAUL — For Minnesota Republicans, this weekend’s convention in Rochester won’t deliver a typical knockout punch to all of the candidates who fail to get the endorsement of the party faithful.

The 2,200 GOP delegates have a bounty of options for governor and U.S. Senate but little expectation of having the final word in selecting the nominees. The break with tradition has caused some worry that the intramural contests will drain resources and cause wounds that make it tougher to defeat a pair of Democratic incumbents who barely won their first races.

Democrats hold their own convention this weekend in Duluth, but with less drama as Gov. Mark Dayton and Sen. Al Franken are virtually assured backing. The party has ample turf to defend: It holds every statewide office and controls both chambers of the Legislature.

Republicans sense opportunity to make inroads. But some activists are riled up because GOP chairman Keith Downey advised local party leaders Wednesday of an obligation to support the candidates endorsed this weekend — a tradition some do not plan to follow.

“As a matter of mutual respect and for the integrity of the party and all involved, if party leader chooses to support a candidate running against the endorsed candidate in any primary, they should first resign their party position unless that party unit’s constitution or bylaws provide otherwise,” Downey wrote in the email, first published by the Politics.MN site run by a former party operative.

Only two Republican gubernatorial contenders have promised to abide by tradition. Hennepin County Commissioner Jeff Johnson and state Sen. Dave Thompson say they’ll drop out if someone else is endorsed. Former state Rep. Marty Seifert is leaving his options open after watching his first attempt at the office end at the 2010 convention. Former House Speaker Kurt Zellers and businessman Scott Honour say they’ll advance to an Aug. 12 primary no matter what and won’t have a large convention presence.

In the Senate race, St. Louis County Commissioner Chris Dahlberg, investment banker Mike McFadden and state Sen. Julianne Ortman have the best shot at the endorsement of delegates, who tend to hold more conservative views than Republicans who don’t attend conventions. McFadden is the only one planning a primary run whatever the convention result. Aside from a possible endorsed rival, he would likely face state Rep. Jim Abeler and other lesser-known candidates.