(Bloomberg) Democrats may lose control of the U.S. House of Representatives in the November elections after contests that will be closer than polls suggest, according to Yale University economist Ray Fair.

Fair, who has developed a formula using economic data that would have correctly predicted all but three presidential elections since 1916, projects that Democrats will get 49.3% of the national vote in this year's congressional races.

"They're going to get less than half of the two-party vote in the House," the professor at the university in New Haven, Conn., said in a telephone interview. "It looks like the election will be relatively close."

Fair's assessment contrasts with polls that show Democrats trailing Republicans by as many as 13 percentage points when voters are asked which party they plan to support.

In a Washington Post-ABC News poll conducted Aug. 30 to Sept. 2, 53% of registered voters said they would vote for the Republican candidate, compared with 40% who backed the Democrat. A CNN-Opinion Research poll of registered voters conducted Sept. 1-2 gave Republicans a 7-percentage- point advantage.

Still Undecided

Still, national polls suggest voters' minds aren't made up.

An Aug. 23-29 Gallup survey of 1,540 registered voters found Republican candidates were preferred over Democrats by 51% to 41%. The Republicans' 10-point lead, the largest in the history of Gallup's midterm congressional election polling, evaporated by the next Gallup survey conducted Aug. 30-Sept. 5.

The latest Gallup poll found hypothetical Republican and Democratic candidates each getting support from 46% of the 1,650 registered voters surveyed.

Republicans, who need a net gain of 39 seats to take control of the 435-member House, are ahead of Democrats by a little less than 2 percentage points, according to Fair's model.

"That could translate into a loss of the House," he said.