With two debates down and two to go, the presidential contest remains a remarkably tight race between candidates with political views that are miles apart.

There is practically no issue — healthcare, immigration, abortion, global warming, national defense and so on — on which President Obama and challenger Mitt Romney do not have stark differences.

Why, then, are polls still in flux? Why is anyone undecided after the seemingly endless months of campaigning and shrill rhetoric?

Part of the answer lies with President Obama’s poor performance in the first debate, which gave Gov. Romney an opening. The president, to be charitable, was off his game.

Gov. Romney has fully exploited the opportunity to reintroduce himself to the electorate as a can-do businessman with a no-nonsense approach to managing the government. Uncommitted voters liked what they saw.

But although the former Massachusetts governor won the debate, the substantial issues have not changed in the larger contest that will be decided on Nov. 6. If anything, the governor’s own statements since then have raised further doubts about his convictions. These are serious enough to give any thinking voter pause if they remain genuinely undecided.

• To cite a recent example: Mr. Romney has painted himself throughout the campaign as “pro-life” (although he was pro-choice as governor of Massachusetts), but on Oct. 9 he said in Iowa that “there is no legislation with regards to abortion that would become part of my agenda.” Then his campaign issued a “clarification” that the governor “would of course support legislation aimed at providing greater protections for life.” All this counts as a double zig-zag.

The governor is entitled to change his views over time — most people do — and even to recalibrate his message as the campaign moves from the primary stage to the general election. Moving to the center is good.

But a pattern of consistent and dramatic changes on the issues raises questions about pandering to voters and a lack of convictions.

• Most important, he has failed to fill in the blanks on his economic plan. The governor’s insistence on cutting taxes rather than taking a balanced approach — raising taxes on those who can afford it and cutting the budget, as well — remains a problem. While he claims his overall tax plan would be revenue-neutral thanks to tax reform, the nonpartisan Tax Policy Center estimates his tax cuts would cost $320 billion by 2015, but he won’t say which “loopholes” he would eliminate to pay for them.

The president doesn’t get a pass on this, either. He failed to embrace the recommendations of his own Simpson-Bowles Commission. He says he also wants lower rates and would simplify the tax code, but hasn’t said how.

• Then there’s healthcare, where the two contenders have radically different views. Republicans would turn Medicare for those who are not at or near retirement into a voucher program, insisting services would not be cut. That sounds like a secret formula for squaring the circle.

Mr. Obama’s plan would cut costs by reducing payments to healthcare providers, again without disturbing services. That, too, sounds dodgy, but at least he has a plan in place, whereas the Romney-Ryan plan remains nebulous.

Either way, there’s plenty more that voters want to know.

The next two debates — next Tuesday and then Oct. 22 at Lynn University in Boca Raton — should illuminate.