The grumbling was evident last week when U.S. Sen. Al Franken turned down an invitation by Minnesota Public Radio to debate his Republican and Independence Party challengers at the Minnesota State Fair.

Conservatives gleefully seized on the opportunity to call him out, and even some Democrats expressed disappointment at their candidate for breaking what many called a 20-year tradition — despite the fact that Franken and former U.S. Sen. Norm Coleman did not debate at the State Fair when vying for the seat six years ago.

Franken’s “Thanks, but no thanks” certainly isn’t the first among this year’s candidates, marking a somewhat slow start to debate season in the run-up to the Aug. 12 primary and Nov. 4 general election. Gov Mark Dayton on Friday also declined an invitation to participate in the MPR State Fair Debate.

A spokesman for businessman Mike McFadden, the GOP-endorsed Senate candidate who still must get through a contested primary, said the campaign was “disappointed” that Franken was unwilling to debate. However, McFadden himself has been called to task by fellow primary candidates for turning down similar invitations.

“I absolutely want to do it, but my opponent seems to not want to debate,” said Rep. Jim Abeler, a 16-year state House veteran who is giving up his seat to vie for the Republican U.S. Senate nomination. “I think people need answers to questions and it helps candidates get stronger,” Abeler said of debates. “The candidates who don’t go to these kinds of forums become weak candidates because they don’t know how to react under pressure.”

McFadden spokesman Tom Erickson said their campaign never intended to take on fellow Republicans.

“We’ve approached this as a race that’s Mike vs. Al Franken,” Erickson said. “That’s how we approached this entire race from day one.”

Franken also has not addressed any of his would-be GOP challengers on the campaign trail. However, the MPR debate he declined is scheduled to take place after the primary.

Franken spokeswoman Alexandra Fetissoff gave no reason why Franken rejected the debate, but she said he will meet with fellow candidates in the future, including at the 2014 Farmfest gathering Aug. 5-7 in Redwood County — long considered a key event for statewide candidates hoping to lock the rural vote.

“Al looks forward to debating, and in fact he’ll be participating in the first forum of the campaign at Farmfest in two weeks,” Fetissoff said in a statement. “Al and former Senator Coleman participated in one MPR debate in 2008 — at the Fitzgerald Theater — and we hope to have a similar opportunity in the fall this time.”

McFadden’s camp said they will be waiting.

“Mike has said since the beginning of 2014 that he’s ready to debate Al Franken any time, any place.” Erickson said.

In the governor’s race, the four candidates vying for the GOP nomination to take on DFL Gov. Mark Dayton are scheduled for at least three debates and forums next week. Businessman Scott Honour, Hennepin County Commissioner Jeff Johnson, former House Minority Leader Marty Seifert and former House Speaker Kurt Zellers are invited to the events. Seifert spokesman Andy Post said his candidate may miss two because of scheduling conflicts. However, he doesn’t view it as a major detriment to the campaign.

“None of the campaigns are jumping at the opportunity to go after each other,” Post said. “Especially if there’s not that much to gain.”

Whoever grabs the nomination may have only a few chances to take on Dayton. Campaign manager Katharine Tinucci said the governor will participate in only six debates, all after Labor Day.

“Six debates are near the top of the usual range for a Minnesota statewide election and more than in virtually every other state,” Tinucci said in a statement. “We believe they will provide Minnesotans with good opportunities to hear and compare the candidates’ views.