How would candidates' tax plans affect investors?

If the universe of dividend stocks shrinks, people who need reliable income would rush into the remaining options. Those would include stocks like utilities, whose regulators sometimes require dividend payouts; and those that must pay out their profits to enjoy lower tax rates, like real estate investment trusts and some energy partnerships.

If many other companies stopped paying dividends, Caplan says, demand for utilities, REITs and energy partnerships could surge, boosting their share prices.

The proposed changes to capital gains rates are unlikely to have much effect on markets or on the economy, several experts said. Caplan calls that debate "a lot of hooting and hollering about nothing." Investment was strong when rates were much higher, before and during Ronald Reagan's presidency, says Caplan, who has managed money almost 35 years.

It's nearly impossible to plan for either possibility, experts say, because of the political uncertainty around tax policy. Day says that he and other investors are holding off on any tax-related buying and selling.

If it appeared likely that capital gains rates would rise to 20 percent from 15 percent, some people might sell stocks before the end of 2012 to take advantage of the lower rate. But that would only make sense only for people who are planning to sell an investment in the next 12 months, Day says, so the effect would be marginal.

The boost to 20 percent from 15 percent is "just not a huge enough jump," he says.

Eliminating investment taxes on people earning less than $200,000 a year would have little effect, experts agree, because those people tend to sock their available income in tax-protected retirement accounts.

As is the case with much of the campaign rhetoric so close to an election, Obama and Romney are playing up these differences to get voters' attention, said Daniel Alpert, managing partner at Westwood Capital LLC, a New York investment bank.

"The impact on the real economy of lifting capital gains taxes by 5 percent is about nil," Alpert says. For investors big enough to affect the financial system, he said, "The problem isn't that people aren't investing, or aren't incented to invest — the problem is, there isn't a whole lot that actually warrants investment."

Daniel Wagner can be reached at www.twitter.com/wagnerreports .