Billionaire Koch brothers target of Democrats' $3M ad campaign

November's congressional mid-term elections are still seven months away, but they're shaping up to be the most expensive ever. Outside groups and the parties themselves have already spent nearly $340 million, and one of the best-known families in big money politics is once again in the spotlight.

The Koch brothers, both in their 70s, are two of the wealthiest men in America. They've been giving to conservative causes for a long time, but now Democrats are trying to make them public enemy No. 1.

On Capitol Hill, the Koch brothers are on every Democrat's lips -- and particularly the Senate's top Democrat's, Harry Reid, of Nevada. He mentions them in almost every speech, calling them "shadowy" and "un-American."

David and Charles Koch are the businessmen behind Koch Industries, a Kansas-based conglomerate that employs 100,000 people and brings in $115 billion annually.

The brothers are also the chief backers of Americans for Prosperity, a powerful political action committee that spent $122 million in 2012, and $30 million just since last year -- mostly targeting the president and vulnerable Senate Democrats.

So now, Democrats are trying to turn the tables with their own $3 million ad campaign against two men who have never held elective office.

Tim Phillips, who runs the Koch-backed group, argues that the left has their own big donors. He said, "It's hypocritical when Harry Reid takes millions of dollars from billionaires on the left to attack folks of resources on the free market side."

A recent bipartisan poll found 52 percent of Americans have never heard of the Koch brothers.

Republican pollster Ed Goeas, who conducted the survey, says Democrats are simply trying to fire up their base. "It's basically giving them a bad guy that they're going out to vote against as opposed to voting on the record, which at this point does not look very good for the president," he said.

Goeas said Republicans employed a similar strategy 10 years ago against progressive billionaire George Soros.

"We don't do it anymore, so that pretty much tells you how that went," Goeas said. "It ended up not mattering to people."

Goeas' poll found a seven-point enthusiasm gap between Republican and Democratic voters, which means Democratic voters were less fired up, CBS News' Nancy Cordes noted. That's why Democratic leaders, she said, are working now to rile them up because that turnout could be the difference between holding on to control of the Senate or losing it.