You can't buy love. Usually not elections, either.

Money can buy lots of things – but political victory might not be one of them.

That’s right. For all the talk about huge donations flowing into the 2010 midterm elections, there’s not a lot of hard evidence that blotting out the sun with paid political ads leads to a seat in Congress or a statehouse. There is some evidence to the contrary.

Let’s take a look at rich people who ran for office in the recent campaign. Take Meg Whitman, the former chief executive officer of eBay, who was the Republican candidate for California governor. Or rather, take her money, if you’re a consultant. She spent $160 million, of which $141 million came from her own pocket. She lost to Democrat Jerry Brown, whose campaign spent a tad less than one-third as much.

According to OpenSecrets.org, a campaign finance watchdog group, 58 House or Senate candidates spent more than a half-million dollars of their own money on their runs for office. About 80 percent of these folks lost.

No, what a candidate may need is not cash by the truckful, but enough money. In other words, after you’ve spent a basic amount introducing yourself to voters and (maybe) attacking your opponent, each extra dollar does not add much.

“Money doesn’t win it for you ... you have to have sufficiency or adequacy,” said former Bush political guru Karl Rove in a broadcast interview last October.

(Note to Democrats: Just because he is Karl Rove, and is involved with advocacy groups that steer money to Republicans, does not mean he’s wrong. A nonpartisan group that favors public financing of elections studied this subject in depth several years ago and reached the same conclusion.)

The Americans for Campaign Reform study looked at the relationship between campaign spending and election outcomes for House races from 1992 to 2006. It found that such elections have a money threshold. Too little cash, and unknown challengers remain unknown. Beyond the threshold, however, “additional spending produces diminishing marginal returns,” according to the group’s 2008 report.