After state officials said Wednesday that rates on the MNsure health insurance exchange will increase an average of 4.5 percent, Democrats praised what they called a modest rise while Republicans seized on the figure, calling it "bogus" and "deceptive."

In a short address with reporters, Gov. Mark Dayton said the rise in the average rate was "predominately good news," praising Minnesota for having among the lowest insurance premiums in the country, according to state officials.

State Senate Minority Leader David Hann, R- Eden Prairie, and Rep. Joe Hoppe, R-Chaska, delivered the response for Republicans. Hann attacked the 4.5 percent figure, arguing that it masks what are larger rate increases for certain plans, participants and regions.

The MNsure rates releases comes hours before Gov. Dayton and GOP challenger Jeff Johnson are set to square off the first gubernatorial debate of the election cycle. In statement, Johnson criticized Dayton for what he called a failure to deliver on a promise that MNsure would decrease the cost of health insurance for middle-class Minnesotans.

"Time and time again, Mark Dayton has failed to deliver on his promises to middle-class Minnesotans," Johnson said. "In fact, the only promises he's kept are the ones he's made to the special interest groups who fund his campaign."

Wednesday's rise in the average rate was no surprise, according to analysts. That's partly because PreferredOne, the Golden Valley-based insurer, announced last month it would leave MNsure and not sell policies for 2015, according to Commerce Commissioner Mike Rothman. PreferredOne currently offers the lowest-cost options on MNsure.

Prior to Wednesday's announcement, health insurance experts pointed to other factors also could be driving premium increases. MNsure will withhold a larger share of premiums next year to cover the cost of the exchange. Health costs are growing, in general, and more patients with costly health problems likely will move from a state safety net program to MNsure.