You might recall that President Obama harbors no love for Rep. Paul Ryan after the wonkish congressman sliced apart Obamacare during the 2010 health care summit.

And, of course, the president and the Democrats spent the entire 2010 campaign running against Ryan's budget plan -- including a commercial that featured a Ryan lookalike pushing an old woman in a wheel chair over a cliff.

So, the Obama campaign's first reaction to hearing the news about Ryan being chosen as Romney's running mate was both typical and predictable.

Politico:

"In naming Congressman Paul Ryan, Mitt Romney has chosen a leader of the House Republicans who shares his commitment to the flawed theory that new budget-busting tax cuts for the wealthy, while placing greater burdens on the middle class and seniors, will somehow deliver a stronger economy," Obama campaign manager Jim Messina said in a statement e-mailed to reporters.

"The architect of the radical Republican House budget, Ryan, like Romney, proposed an additional $250,000 tax cut for millionaires, and deep cuts in education from Head Start to college aid. His plan also would end Medicare as we know it by turning it into a voucher system, shifting thousands of dollars in health care costs to seniors. As a member of Congress, Ryan rubber-stamped the reckless Bush economic policies that exploded our deficit and crashed our economy. Now the Romney-Ryan ticket would take us back by repeating the same, catastrophic mistakes," Messina added.

They can continue to berate Ryan and Romney over the budget plan, but by doing so, they highlight the fact that they have no plan of their own. This is why the choice of Ryan is important. The fundamentals of the campaign have shifted dramatically in Romney's favor. From a contest where personality and class warfare dominated to one that will feature a geniune debate about two political philosophies, the Obama campaign must now engage on a whole other level.

There will still be attacks, but by the time November rolls around, the American people are going to have a clear choice.