HEMPSTEAD, N.Y. — President Barack Obama and Republican Mitt Romney face off Tuesday in a “town hall” style debate that has the potential to finally break the race’s stubborn tie as their battle roars into its final, decisive three weeks.

The 90-minute debate at Hofstra University, which begins at 9 p.m. EDT, comes with the two men neck and neck after Romney bested Obama in their first debate, gained in the polls and climbed back into contention. The result could hinge on the way the two men perform, but also on a format that will allow members of the audience to pose questions, with follow-ups from moderator Candy Crowley of CNN.

Obama, sharply criticized for a listless performance in the first presidential debate on Oct. 3, is expected to more aggressively question Romney’s shifts in tone and position over the years — and in some cases recent days — on tax cuts, immigration, abortion and other subjects.

“We saw this clearly in the first presidential debate on Oct. 3, as Gov. Romney cynically and dishonestly hid the self-described ‘severely conservative’ positions he’s been running on — and there’s no doubt he’s memorizing more deceptions as he prepares for Tuesday’s second debate,” Obama campaign manager Jim Messina said in a memo Monday.

Obama, who has been practicing in Williamsburg, Va., is expected to press Romney hard on the Republican’s contention that he can cut current income tax rates 20 percent across the board without increasing the federal deficit.

Romney, who has been preparing in the Boston area, is expected to counter not only with a vigorous defense of his plan but with a recitation of economic woes that he says the Obama administration has helped exacerbate. The more informal town hall format is likely to be more comfortable for the affable Romney.

Campaigning in Ohio, Republican vice presidential candidate Paul Ryan previewed a likely line of attack for Tuesday, ripping the president on unemployment, budget deficits and long-term problems in Medicare.