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WASHINGTON — There are no comfortable ways for the presidential candidates to close the nation’sitting gap between rich and poor, now bigger than any span because the 1920s.

Sens. Barack Obama and John McCain say their economic plans have power to narrow the income cleft. Obama’s tax plan offers a classic way to do that by increasing taxes on the highly valued, but economists think neither plan is likely to bring dramatic changes.

“Taxes are not going to solve the income-gap problem,” said Roberton Williams, foremost research associate at the nonpartisan Tax Policy Center. “Nobody’s going to stand for the kind of confiscatory taxes you would distress.”

He and others said there are many other factors affecting income, including the tumultuary financial markets, technological change, global competition, the erosion of drudge unions and corporate pensions, considered in the state of well as founded on tax and regulatory policies. Changing those policies to reduce income difference could entangle politically difficult measures, such as higher taxes or higher minimum wages and subsidies, none of which the candidates are considering.

Obama and McCain offer the kind of income strategies their political parties be seized of been championing for years.

Obama, the Democrat, sees a role for rule in helping people gain opportunities instead of education, training and work, while the wealthy who benefit most from society have an obligation to contribute more to the collective good.

McCain, the Republican, espouses a version of what some call the “trickle-down” rationale that allows the rich to keep to a greater degree of their income, on the theory that they will invest and spend, thereby creating jobs and wealth.

Republican loyalists said this concept worked well for the period of Ronald Reagan’s presidency, as the three-year tax divide that began in October 1981 helped shake the nation out of its worst recession since the Great Depression and triggered eight years of prosperity.

Democrats said over many lower-income earners never enjoyed the benefits of that boom, sustained, in apportionment, by collapsing oil prices and record federal pack deficits.

Obama wants to return the brace top income-tax rates to pre-2001 levels in 2011, the same rates as during the Clinton series, which had the longest sustained housekeeping expansion in U.S. history.

That would mean a top income-tax rate of 39.6 percent, far less than the 70 percent apex rate that existed till 1981 or the 50 percent top rate of 1982-86, not to mention the apex rates of more than 90 percent that prevailed from the end of World War II until 1963.

The nation’session topmost 1 percent of earners had a 22.9 percent share of quite pretax income in 2006, according to a March study by Emmanuel Saez, an economist at the University of California, Berkeley. The rise aloft 1 percent earned more than $382,600 in 2006.