NASHUA, N.H. -- President Obama unfurled bare-knuckled criticism against opposition Republicans on Tuesday, painting them as electoral opportunists willing to switch positions at will to score points with voters. 

The president's fellow Democrats have been pleading with him, as de facto leader of his party, to get tougher on Republicans leading into this fall's midterm congressional and gubernatorial elections. Those calls increased with the Democrats' stunning loss two weeks ago of a Senate seat in Massachusetts, seen as an indictment of Democratic leadership in Washington and a potential bellwether for the party in the voting later this year. 

Obama answered those calls in New Hampshire, where two House seats and a Senate seat are in play in November. The state figures prominently in presidential elections because of its first-in-the-nation primary and its tradition of involved, informed residents. 

Obama made a play for bipartisanship, urging Congress' minority Republicans to cooperate with him and Democratic leadership on overhauling the nation's education, energy and health care policies and on tackling record and crippling federal budget deficits. 

"Democrats can't do this alone nor should we," Obama said. 

Yet as he reached out with one hand, he slapped with the other. Obama took Republicans to task for two instances of switching positions. 

He said that those who opposed last year's massive stimulus package, and have argued since that it isn't helping to save or create jobs, have also claimed credit in their districts for projects that were funded by the bill. "They've found a way to have their cake and vote against it too," Obama said, without naming any lawmakers specifically. 

Obama also criticized Republicans for opposing a bill to create a bipartisan commission on reducing the deficit, saying that seven GOP senators who once co-sponsored the bill then voted against it. 

"It's one thing to have an honest difference of opinion on something," Obama said. "It's another to walk away from your responsibilities to confront the challenges facing this country because you think it's good short-term politics." 

He added: "You're out of patience for this kind of business as usual."